阅读说明：本技术 一种大功率快恢复二极管结构 (High-power fast recovery diode structure ) 是由 王俊 岳伟 俞恒裕 梁世维 刘航志 江希 杨余 于 2021-08-02 设计创作，主要内容包括：本发明公布了一种大功率快恢复二极管结构,其特征在于,从上至下依次设置有第一电极层、第二导电类型的导通二区、第一导电类型的阻断层、第一导电类型的导通三区和第二电极层,所述导通二区的上表面嵌入多个第二导电类型的导通一区,多个所述导通一区间隔设置；所述导通一区和导通二区的上表面与第一电极层接触；所述导通二区的下表面与阻断层接触；所述阻断层与导通三区之间还设置有第一导电类型的过渡区；所述过渡区的下表面与导通三区连接；所述过渡区的上表面及侧面与阻断层连接。本发明高度集成,可以改善二极管阻断区载流子的分布,在提升快恢复二极管的反向恢复特性的前提下降低其正向导通压降。(The invention discloses a high-power fast recovery diode structure which is characterized in that a first electrode layer, a second conduction type conduction area, a first conduction type blocking layer, a first conduction type conduction area and a second electrode layer are sequentially arranged from top to bottom, a plurality of second conduction type conduction areas are embedded into the upper surface of the second conduction area, and the conduction areas are arranged at intervals; the upper surfaces of the first conducting area and the second conducting area are in contact with the first electrode layer; the lower surface of the second conducting area is in contact with the blocking layer; a transition region of the first conduction type is also arranged between the blocking layer and the conduction three region; the lower surface of the transition region is connected with the three conducting regions; the upper surface and the side surface of the transition region are connected with the blocking layer. The invention has high integration, can improve the distribution of carriers in the diode blocking region, and reduces the forward conduction voltage drop of the fast recovery diode on the premise of improving the reverse recovery characteristic of the fast recovery diode.)

1. A high-power fast recovery diode structure is characterized in that a first electrode layer (1), a second conduction type conduction area (3), a first conduction type blocking layer (4), a first conduction type conduction area (6) and a second electrode layer (7) are sequentially arranged from top to bottom, a plurality of first conduction type conduction areas (2) are embedded in the upper surface of the second conduction area (3), and the plurality of first conduction areas (2) are arranged at intervals; the upper surfaces of the first conducting area (2) and the second conducting area (3) are in contact with the first electrode layer (1); the lower surface of the second conduction region (3) is contacted with the blocking layer (4); a transition region (5) of the first conduction type is also arranged between the blocking layer (4) and the conduction three region (6); the lower surface of the transition region (5) is connected with the conduction three region (6); the upper surface and the side surface of the transition region are connected with the blocking layer.

2. A high power fast recovery diode structure according to claim 1, characterized in that the doping concentration of said transition region (5) is greater than the doping concentration of said blocking layer (4), and the doping concentration of said transition region (5) is less than the doping concentration of said conducting region (6).

3. A high power fast recovery diode structure as claimed in claim 2, characterized in that the doping concentration of said transition region (5) increases in the longitudinal direction.

4. A high power fast recovery diode structure according to claim 3, wherein said transition region (5) comprises a first transition region (51) and a second transition region (52), said first transition region (51) and said second transition region (52) being sequentially juxtaposed in the longitudinal direction; the upper surface and the side surface of the first transition area (51) are connected with the blocking layer (4), and the upper surface of the second transition area (52) is connected with the blocking layer (4); the lower surface of the second transition region (52) is connected with the third conduction region (6); the doping concentration of the first transition region (51) is less than that of the second transition region (52); the doping concentration of the first transition area (51) is greater than that of the blocking layer (4), and the doping concentration of the second transition area (52) is less than that of the third conduction area (6).

5. A high power fast recovery diode structure as claimed in claim 2, characterized in that the doping concentration of said transition region (5) increases in the lateral direction.

6. The high-power fast recovery diode structure according to claim 5, wherein the transition region comprises a first transition region (51), a second transition region (52) and a third transition region (53), and the first transition region (51), the second transition region (52) and the third transition region (53) are sequentially arranged in parallel along a transverse direction; the upper surfaces of the three transition areas (53) and the two transition areas (52) are connected with the blocking layer (4), and the lower surfaces of the three transition areas (53) and the two transition areas (52) are connected with the three conducting areas (6); the upper surface and the side surface of the first transition area (51) are connected with the blocking layer (4), and the lower surface of the first transition area (51) is connected with the three conducting areas (6); the doping concentration of the transition three region (53) is greater than that of the transition two region (52); the doping concentration of the second transition region (52) is greater than that of the first transition region (51); the doping concentration of the first transition region (51) is greater than that of the blocking layer (4), and the doping concentration of the third transition region (53) is less than that of the third conducting region (6).

7. A high power fast recovery diode structure according to claim 1 wherein the doping concentration of said conducting one region (2) is greater than the doping concentration of said conducting two region (3).

8. A high power fast recovery diode structure according to claim 7, characterized in that the doping concentration of said conducting first region (2) and the doping concentration of said conducting second region (3) decrease in the longitudinal direction.

9. The high power fast recovery diode structure of claim 1, wherein said first conductivity type is N-type conductivity and said second conductivity type is P-type conductivity.

Technical Field

The invention belongs to the technical field of semiconductors, and particularly relates to a high-power fast recovery diode structure.

Background

The power electronic technology is based on a power semiconductor device, and is a technology for converting and controlling electric energy by combining weak current control and strong current operation. The power electronic technology is widely applied to the fields of general industry, transportation, electric power systems, power supply application and household electrical appliances.

As a core of power electronics, power semiconductor devices play a decisive role in the overall value, size, weight and technical development of power electronics. Modern power electronic devices are still developing towards high power, easy driving and high frequency. Power electronics technology has prompted power semiconductor devices to continue to improve performance, mainly in several areas: (1) higher power, higher on current and reverse withstand voltage; (2) lower power consumption, lower conduction voltage drop and reverse leakage current; (3) higher frequency, faster switching speed and lower switching losses; (4) higher requirements are placed on the stability of the device.

With the development of power electronic technology, the application of various frequency conversion circuits and chopper circuits is continuously expanded, and the main loop of the power electronic circuits adopts a thyristor switched off by a circulating current or adopts novel power electronic devices with self-turn-off capability, such as GTO, MCT, IGBT and the like, and a fast diode connected in parallel with the main loop is required to reduce the charging time of a capacitor through the reactive current in a load and simultaneously restrain the high voltage induced by the instantaneous reversal of the load current. As the switching speed of these devices continues to increase, the diodes must have the ability to turn on and off quickly in order to match their turn-off process. The reverse recovery capability of the diode is mainly required by the following aspects: 1) short reverse recovery time; 2) a smaller reverse recovery current; 3) soft recovery characteristics.

The fast soft recovery diode is a PIN diode. Different from a common P-N junction diode, the PIN diode is additionally provided with an intrinsic layer (low doped layer) between P + and N + at two ends, and the whole structure is divided into three parts, namely a P + region, an intrinsic region and an N + region.

Like a normal p-n diode, this diode is also a bipolar device. The intrinsic layer in the middle of the PIN diode can enable the PIN diode to bear high reverse voltage, and the thickness and the doping concentration of the intrinsic layer directly determine the voltage-resistant grade of the diode. When the diode is conducted in the forward direction, the N + region and the P + region with high doping concentration at the two ends can inject a large amount of free carriers into the intrinsic region of the diode, so that a conductivity modulation effect is generated in the intrinsic region, and a lower forward conduction voltage drop of the device is maintained. However, when the PIN diode is switched from the on state to the off state, free carriers in the intrinsic region cannot be immediately recombined. Free carriers are extracted from the intrinsic region to form an inverted peak current, the inverted recovery current. The di/dt of the current is large, which causes overvoltage surge of a circuit, increase of self turn-off loss of a device, and deterioration of switching characteristics and reliability.

In order to reduce the diode reverse recovery current and di/dt to achieve soft recovery, there is a patent that adds a transition region to the blocking region of the diode. The transition region is a heavily doped N-type region and is located on the cathode side of the blocking region. Its doping concentration is sufficiently large that this portion is not depleted by the reverse bias on the diode during reverse recovery. At the same time, the doping concentration of the transition region is low enough to allow conductivity modulation, so that there is some stored charge in the transition region. In the fourth stage of reverse recovery, the applied bias cannot rapidly extract the portion of stored charge to reduce the rate of change of the reverse recovery current. Therefore, in the design process of the FRD, the dynamic performance and the static performance of the FRD cannot be optimized in a good direction at the same time, and the performance of one side can be optimized only under the condition of sacrificing the performance of the other side. In general, in order to improve the softness of the diode and avoid the rapid extraction of carriers during the reverse recovery stage of the diode, the length of the diode blocking region needs to be increased to enhance the storage capability of the carriers, so as to form a non-punch-through diode, thereby achieving the soft recovery effect. However, this causes the forward conduction voltage drop of the diode to increase, and the conduction loss of the diode greatly increases. On the other hand, the transition region may be arranged such that part of the free carriers are not depleted, but the concentration of the transition region cannot be set too large in order to satisfy the conductance modulation effect. The provision of the transition region is therefore not particularly significant for improving the forward conduction voltage drop of the diode.

Disclosure of Invention

The invention aims to solve the problems and provides a high-power fast recovery diode structure which is highly integrated, can improve the distribution of carriers in a diode blocking region and reduces the forward conduction voltage drop of the fast recovery diode on the premise of improving the reverse recovery characteristic of the fast recovery diode.

In order to realize the purpose, the invention adopts the technical scheme that:

a high-power fast recovery diode structure is characterized in that a first electrode layer, a second conduction type conduction area, a first conduction type blocking layer, a first conduction type conduction area and a second electrode layer are sequentially arranged from top to bottom, a plurality of first conduction type conduction areas are embedded in the upper surface of the second conduction area, and the plurality of first conduction areas are arranged at intervals; the upper surfaces of the first conducting area and the second conducting area are in contact with the first electrode layer; the lower surface of the second conducting area is in contact with the blocking layer; a transition region of the first conduction type is also arranged between the blocking layer and the conduction three region; the lower surface of the transition region is connected with the three conducting regions; the upper surface and the side surface of the transition region are connected with the blocking layer.

Preferably, the doping concentration of the transition region is greater than that of the blocking layer, and the doping concentration of the transition region is less than that of the conduction region.

Preferably, the doping concentration of the transition region increases in the longitudinal direction.

Preferably, the transition area comprises a first transition area and a second transition area, and the first transition area and the second transition area are sequentially arranged in parallel along the longitudinal direction; the upper surface and the side surface of the first transition area are connected with a blocking layer, and the upper surface of the second transition area is connected with the blocking layer; the lower surface of the second transition area is connected with the third conduction area; the doping concentration of the first transition region is less than that of the second transition region; the doping concentration of the first transition area is greater than that of the blocking layer, and the doping concentration of the second transition area is less than that of the third conduction area.

Preferably, the doping concentration of the transition region increases in the lateral direction.

Preferably, the transition zone comprises a first transition zone, a second transition zone and a third transition zone, and the first transition zone, the second transition zone and the third transition zone are sequentially arranged in parallel along the transverse direction; the upper surfaces of the transition three area and the transition two area are connected with a blocking layer, and the lower surfaces of the transition three area and the transition two area are connected with the conduction three area; the upper surface and the side surface of the first transition area are connected with the blocking layer, and the lower surface of the first transition area is connected with the three conducting areas; the doping concentration of the transition three area is greater than that of the transition two area; the doping concentration of the second transition region is greater than that of the first transition region; the doping concentration of the first transition area is greater than that of the blocking layer, and the doping concentration of the third transition area is less than that of the third conduction area.

Preferably, the doping concentration of the first conducting region is greater than that of the second conducting region.

Preferably, the doping concentration of the first conducting region and the doping concentration of the second conducting region decrease in the longitudinal direction.

Preferably, the first conductivity type is an N-type conductivity material, and the second conductivity type is a P-type conductivity material.

The invention has the beneficial effects that:

under the condition that the diode is normally conducted, holes at the PN junction are mainly provided by the low-doped region of the conducting two regions, and the free carrier concentration of the blocking region close to the PN junction is small, so that the peak value of the reverse recovery current of the diode can be remarkably reduced, and the reverse recovery time of the diode is shortened. Meanwhile, the high-doping area of the transition area is responsible for the passing of current, and the forward conduction voltage drop on the transition area is small due to the high concentration of the high-doping area; the low-doped region of the transition region is responsible for storing free carriers during forward conduction, and the free carriers in the region provide soft recovery current of the diode during the reverse recovery of the diode. In case of a surge current, holes at the PN junction are provided by a highly doped region that turns on a region. Compared with the normal conduction, the free current carriers at the PN junction are greatly increased, so that the surge current is effectively resisted.

Drawings

Fig. 1 is a schematic structural diagram of embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of embodiment 3 of the present invention.

Fig. 4 is a comparison graph of the maximum reverse recovery voltage-forward conduction voltage drop compromise optimization curve of the diode and the conventional diode.

Fig. 5 is a diagram comparing the forward conduction of the present invention with that of a conventional diode.

Fig. 6 is a graph comparing the reverse recovery of the present invention with a conventional diode.

Reference numbers in the drawings: 1. a first electrode layer; 2. conducting a region; 3. conducting the second area; 4. a blocking layer; 5. a transition zone; 51. a transition first zone; 52. a transition second zone; 53. conducting three zones; 6. conducting three zones; 7. a second electrode layer.

Detailed Description

The following detailed description of the present invention is given for the purpose of better understanding technical solutions of the present invention by those skilled in the art, and the present description is only exemplary and explanatory and should not be construed as limiting the scope of the present invention in any way.

Example 1

As shown in fig. 1, a high-power fast recovery diode structure is sequentially provided with a first electrode layer 1, a second conduction type conduction area 3, a first conduction type blocking layer 4, a first conduction type conduction area 6 and a second electrode layer 7 from top to bottom, wherein a plurality of first conduction type conduction areas 2 are embedded in the upper surface of the second conduction area 3, and the plurality of first conduction areas 2 are arranged at intervals; the upper surfaces of the first conducting region 2 and the second conducting region 3 are in contact with the first electrode layer 1; the lower surface of the second conduction area 3 is contacted with the blocking layer 4; a transition region 5 of the first conduction type is also arranged between the blocking layer 4 and the conduction three region 6; the lower surface of the transition region 5 is connected with the conduction region 6; the upper surface and the side surface of the transition region are connected with the blocking layer.

In the present embodiment, the doping concentration of the transition region 5 is greater than that of the blocking layer 4, and the doping concentration of the transition region 5 is less than that of the conduction region 6.

In a specific implementation, the intrinsic carrier concentration of the blocking region 4 is small, which is beneficial for the conductivity modulation effect and thus for the storage of free carriers, which provides a soft reverse recovery for the diode. The intrinsic concentration of the transition region 5 is relatively large and the storage capacity for free carriers is relatively weak but the advantage is that the on-resistance is small. In the conventional diode, good compromise between forward conduction and reverse recovery performance of the device is difficult to realize, but the high-concentration transition region 5 and the low-concentration blocking region 4 are arranged in parallel, current conduction is mainly carried out by the transition region 5, and reverse recovery is mainly carried out by the blocking region 4, so that compromise conditions required by forward conduction and reverse recovery of the diode are considered.

In the present embodiment, the doping concentration of the transition region 5 increases in the longitudinal direction, that is to say that a high concentration region and a low concentration region are present simultaneously on the transition region 5.

In the present embodiment, the doping concentration of the first conducting region 2 is greater than the doping concentration of the second conducting region 3.

In the present embodiment, the doping concentration of the first conducting region 2 and the doping concentration of the second conducting region 3 decrease in the longitudinal direction.

In the present embodiment, the first conductive type is an N-type conductive type material, and the second conductive type is a P-type conductive type material.

In a specific embodiment, the first electrode layer 1 is an anode metal, the second electrode layer 7 is a cathode metal, the first conductivity type is an N-type conductivity type material, and the second conductivity type is a P-type conductivity type material, that is, the first conducting region 2 of the second conductivity type is a P + type high-concentration doped low-resistance region, the second conducting region 3 of the second conductivity type is a P-type higher-concentration doped low-resistance region, the blocking layer 4 of the first conductivity type is an N-type low-concentration doped high-resistance region, the third conducting region 6 of the first conductivity type is an N + type low-resistance region, and the transition region 5 is an N-type transition region.

In this embodiment, the doping concentration of the conducting second region 3 is less than the doping concentration of the conducting first region 2, and when the current is normally conducted, the hole carriers of the blocking region are mainly provided by the conducting second region 3, and the concentration of the hole carriers is low, so that the hole carriers provided are fewer, which is beneficial to the extraction of the carriers by the diode reverse recovery, and the speed of the diode reverse recovery is increased, thereby shortening the reverse recovery time of the diode. When the diode encounters high surge current, the high-concentration conduction region 2 works, and a large number of hole carriers are injected into the blocking region, so that the body resistance of the diode is reduced, the surge current resistance of the diode is enhanced, and the peak value of the reverse recovery current of the diode can be obviously reduced. Meanwhile, the highly doped region of the transition region 5 is responsible for the passing of current, and the forward conduction voltage drop on the transition region 5 is small due to the high concentration of the highly doped region; the low doped region of the transition region 5 is responsible for the storage of free carriers during forward conduction, and during the reverse recovery of the diode, the free carriers in this region provide the soft recovery current of the diode. In case of surge current, holes at the PN junction are provided by the highly doped region of the conducting two region. Compared with the normal conduction, the free current carriers at the PN junction are greatly increased, so that the surge current is effectively resisted.

Example 2

As shown in fig. 2, a high-power fast recovery diode structure is sequentially provided with a first electrode layer 1, a second conduction type conduction area 3, a first conduction type blocking layer 4, a first conduction type conduction area 6 and a second electrode layer 7 from top to bottom, wherein a plurality of first conduction type conduction areas 2 are embedded in the upper surface of the second conduction area 3, and the plurality of first conduction areas 2 are arranged at intervals; the upper surfaces of the first conducting region 2 and the second conducting region 3 are in contact with the first electrode layer 1; the lower surface of the second conduction area 3 is contacted with the blocking layer 4; a transition region 5 of the first conduction type is also arranged between the blocking layer 4 and the conduction three region 6; the lower surface of the transition region 5 is connected with the conduction region 6; the upper surface and the side surface of the transition region are connected with the blocking layer.

In the present embodiment, the doping concentration of the transition region 5 is greater than that of the blocking layer 4, and the doping concentration of the transition region 5 is less than that of the conduction region 6.

In the present embodiment, the doping concentration of the transition region 5 increases gradually along the longitudinal direction, the transition region 5 includes a first transition region 51 and a second transition region 52, and the first transition region 51 and the second transition region 52 are sequentially arranged in parallel along the longitudinal direction; the upper surface and the side surface of the first transition area 51 are connected with the blocking layer 4, and the upper surface of the second transition area 52 is connected with the blocking layer 4; the lower surface of the second transition area 52 is connected with the third conduction area 6; the doping concentration of the first transition region 51 is less than that of the second transition region 52; the doping concentration of the first transition region 51 is greater than that of the blocking layer 4, and the doping concentration of the second transition region 52 is less than that of the third conduction region 6.

In the present embodiment, the doping concentration of the first conducting region 2 is greater than the doping concentration of the second conducting region 3, and the doping concentration of the first conducting region 2 and the doping concentration of the second conducting region 3 decrease in the longitudinal direction.

In the present embodiment, the first conductive type is an N-type conductive type material, and the second conductive type is a P-type conductive type material.

In a specific embodiment, the first electrode layer 1 is an anode metal, the second electrode layer 7 is a cathode metal, the first conductivity type is an N-type conductivity type material, the second conductivity type is a P-type conductivity type material, that is, the first conducting region 2 of the second conductivity type is a P + type high-concentration doped low-resistance region, the second conducting region 3 of the second conductivity type is a P-type higher-concentration doped low-resistance region, the blocking layer 4 of the first conductivity type is an N-type low-concentration doped high-resistance region, the third conducting region 6 of the first conductivity type is an N + type low-resistance region, the first transition region 51 is an N-transition region, and the second transition region 52 is an N-type transition region. The first conducting area 2 and the second conducting area 3 are front conducting layers of the diode structure, and the third conducting area 6 is a back conducting layer.

To illustrate the effect of the transition region in the structure of the present invention, two diode structures were designed for simulation comparison. The transition region of the conventional diode is a complete and integral layer, there is no lateral contact with the blocking region, and the concentration of the transition region of the conventional diode varies only in a direction perpendicular to the PN junction, and the concentration of the conventional diode is constant in a direction parallel to the PN junction. Firstly, fixing a front conducting layer, a blocking layer and a back conducting layer of two diodes unchanged, wherein one conventional diode adopts a traditional transition layer, and the concentration of the transition region is increased progressively along the direction from the blocking layer 4 to the back conducting layer; the transition layer of the other diode is the transition region 5 structure of the present invention.

First, reverse recovery simulation is performed on two diodes by using TCAD, as shown in FIG. 6, it can be seen that the reverse recovery peak currents of the two diodes are the same, but the diode reverse recovery softness of the structure of the invention is better than that of the conventional diode. Forward conduction simulations were then performed for both diodes.

As shown in fig. 5, the forward conduction voltage of the diode of the structure of the present invention almost matches the forward conduction voltage of the conventional diode. The simulation comparison shows that: the diode with the structure of the invention improves the softness of reverse recovery under the condition of not damaging the forward conduction characteristic. This shows that the diode with the structure of the invention has better optimization prospect compared with the conventional diode. Under the condition that the front conducting layer, the blocking layer and the back conducting layer of the diode are fixed, the doping concentration of the transition first region 51 is set to be the concentration value of the blocking region. And changing the doping concentration of the second transition region 52, recording the maximum reverse voltage borne by the diode under the same reverse recovery test circuit, and simultaneously testing the forward conduction voltage drop of the diode in normal operation. The compromise optimization curve of the reverse recovery maximum voltage-forward conduction voltage drop shown in fig. 5 is made and compared with the compromise optimization curve of the reverse recovery maximum voltage-forward conduction voltage drop of the diode in the conventional transition region.

As shown in fig. 4, for the diode with the conventional structure, increasing the doping concentration of the transition region can reduce the forward conduction voltage drop, but the transition region with the higher doping concentration cannot store the free carriers well, so that the diode can easily deplete the free carriers at the end of the reverse recovery, so that the reverse recovery current is rapidly reduced, the diode bears a considerable reverse recovery voltage, and the diode generates a severe oscillation between the reverse recovery current and the voltage. The transition region 5 of the structure is divided into a first transition region 51 and a second transition region 52, and the second transition region 52 with higher doping concentration is responsible for flowing most of conduction current to ensure the forward conduction voltage drop of the diode. The transition first region 51 with lower doping concentration is responsible for storing free carriers stored during forward conduction, and the softness of the reverse recovery of the diode is ensured. As can be seen from fig. 4, the diode with the structure of the present invention has smaller maximum reverse voltage than the conventional diode under the same forward conduction voltage drop. And the diode with the structure of the invention has no inflection point of the sudden increase of the maximum reverse voltage, which shows that the diode is always soft recovery. Compared with the traditional diode, the diode with the structure has a better compromise optimization curve and a larger optimization space.

In the normal turn-on stage of the device, because the doping concentration of the conducting second region 3 is lower, the free carrier concentration of the blocking region 4 near the anode is smaller than that near the cathode, at this time, most of the conducting current flows through the transition second region 52, the transition first region 51 stores a large amount of free carriers, and because the doping concentration of the transition second region 52 is higher, the conducting voltage of the diode is lower. During the reverse recovery of the device, the free carriers near the anode determine the current peak value Irr of the reverse recovery, and because the carrier concentration near the anode is low in the device, compared with the conventional diode, the structure can remarkably reduce the current peak value Irr of the reverse recovery and the reverse recovery charge Qrr, thereby accelerating the reverse recovery of the diode and reducing the loss of the reverse recovery of the diode. At the end of reverse recovery, the free carriers of the conventional diode are completely consumed by an electric field, and the reverse recovery current is quickly attenuated to zero to form larger di/dt, so that the diode bears large reverse recovery voltage, even forms severe electromagnetic oscillation, and causes certain influence on electronic equipment. The current carrier stored in the transition two-zone of the diode structure provided by the invention can not be exhausted by an electric field, and the free current carrier required by the trailing current of the reverse recovery can be provided for the diode at the terminal stage of the reverse recovery of the diode, so that the soft recovery is realized.

Example 3

As shown in fig. 3, a high-power fast recovery diode structure is sequentially provided with a first electrode layer 1, a second conduction type conduction area 3, a blocking layer 4 of a first conduction type, a first conduction type conduction area 6 and a second electrode layer 7 from top to bottom, wherein a plurality of first conduction type conduction areas 2 of the second conduction type are embedded in the upper surface of the second conduction area 3, and the plurality of first conduction areas 2 are arranged at intervals; the upper surfaces of the first conducting region 2 and the second conducting region 3 are in contact with the first electrode layer 1; the lower surface of the second conduction area 3 is contacted with the blocking layer 4; a transition region 5 of the first conduction type is also arranged between the blocking layer 4 and the conduction three region 6; the lower surface of the transition region 5 is connected with the conduction region 6; the upper surface and the side surface of the transition region are connected with the blocking layer.

In the present embodiment, the doping concentration of the transition region 5 is greater than that of the blocking layer 4, the doping concentration of the transition region 5 is less than that of the conduction region 6, and the doping concentration of the second transition region 52 is greater than that of the blocking layer 4.

In this embodiment, the doping concentration of the transition region 5 increases progressively along the lateral direction, wherein the transition region includes a first transition region 51, a second transition region 52 and a third transition region 53, and the first transition region 51, the second transition region 52 and the third transition region 53 are sequentially arranged in parallel along the lateral direction; the upper surfaces of the three transition areas 53 and the two transition areas 52 are connected with the blocking layer 4, and the lower surfaces of the three transition areas 53 and the two transition areas 52 are connected with the three conducting areas 6; the upper surface and the side surface of the first transition area 51 are connected with the blocking layer 4, and the lower surface of the first transition area 51 is connected with the three conducting areas 6; the doping concentration of the transition three region 53 is greater than that of the transition two region 52; the doping concentration of the second transition region 52 is greater than that of the first transition region 51; the doping concentration of the transition one region 51 is greater than that of the blocking layer 4, and the doping concentration of the transition three region 53 is less than that of the conduction three region 6.

In the present embodiment, the doping concentration of the first conducting region 2 is greater than the doping concentration of the second conducting region 3, and the doping concentration of the first conducting region 2 and the doping concentration of the second conducting region 3 decrease in the longitudinal direction.

In the present embodiment, the first conductive type is an N-type conductive type material, and the second conductive type is a P-type conductive type material.

In a specific embodiment, the first electrode layer 1 is an anode metal, the second electrode layer 7 is a cathode metal, the first conductivity type is an N-type conductivity type material, the second conductivity type is a P-type conductivity type material, that is, the first conducting region 2 of the second conductivity type is a P + type high-concentration doped low-resistance region, the second conducting region 3 of the second conductivity type is a P-type higher-concentration doped low-resistance region, the blocking layer 4 of the first conductivity type is an N-type low-concentration doped high-resistance region, the third conducting region 6 of the first conductivity type is an N + type low-resistance region, the first transition region 51 is an N-transition region, the second transition region 52 is an N-type transition region, and the third transition region 53 is an N + type transition region.

In the normal on-state of the device, because the doping concentration of the conducting second region 3 is relatively low, the free carrier concentration of the blocking region 4 near the anode is smaller than that near the cathode, at this time, the conducting current decreases progressively along the directions of the transition three region 53, the transition two region 52, the transition first region 51 and the blocking layer, and the storage amount of the free carriers increases progressively along the directions of the transition three region 53, the transition two region 52, the transition first region 51 and the blocking layer. The forward conduction voltage drop of the diode is relatively small due to the relatively small resistivity of the transition region 53 with high concentration.

During the reverse recovery of the device, the free carriers near the anode determine the current peak value Irr of the reverse recovery, and because the carrier concentration near the anode is low in the device, compared with the conventional diode, the structure can remarkably reduce the current peak value Irr of the reverse recovery and the reverse recovery charge Qrr, thereby accelerating the reverse recovery of the diode and reducing the loss of the reverse recovery of the diode. At the end of reverse recovery, the free carriers of the conventional diode are completely consumed by an electric field, and the reverse recovery current is quickly attenuated to zero to form larger di/dt, so that the diode bears large reverse recovery voltage, even forms severe electromagnetic oscillation, and causes certain influence on electronic equipment. The current carriers stored in the low-concentration transition region and the blocking region of the diode structure can not be exhausted by an electric field, and free current carriers required by the trailing current of the diode can be provided for the diode in the last stage of the reverse recovery of the diode, so that the soft recovery of the diode is realized.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts of the present invention. The foregoing is only a preferred embodiment of the present invention, and it should be noted that there are objectively infinite specific structures due to the limited character expressions, and it will be apparent to those skilled in the art that a plurality of modifications, decorations or changes may be made without departing from the principle of the present invention, and the technical features described above may be combined in a suitable manner; such modifications, variations, combinations, or adaptations of the invention using its spirit and scope, as defined by the claims, may be directed to other uses and embodiments.