阅读说明：本技术 一种局部凹槽结构的AlGaN/GaN HEMT器件 (AlGaN/GaN HEMT device with local groove structure ) 是由 刘静 王琳倩 黄忠孝 于 2019-09-25 设计创作，主要内容包括：本发明公开了一种局部凹槽结构的AlGaN/GaN HEMT器件,包括自下而上依次设置的衬底、缓冲层、势垒层和钝化层,势垒层上表面且位于钝化层左右两端分别设置有源极和漏极,势垒层上表面且位于钝化层中部设置有栅极；势垒层上设置有凹槽结构。缓冲层由厚度为2μm的GaN组成,摻杂浓度为1×10<Sup>15</Sup>cm<Sup>-3</Sup>。势垒层由厚度为0.02μm的AlGaN组成,摻杂浓度为1×10<Sup>17</Sup>cm<Sup>-3</Sup>。钝化层由厚度为0.05μm的Si<Sub>3</Sub>N<Sub>4</Sub>组成。栅极、源极及漏极的长度均为0.5μm。凹槽结构由厚度为50nm的Si<Sub>3</Sub>N<Sub>4</Sub>组成,长度L为1.0μm,高度H为0.010μm,使得电流变化量减小,电流崩塌得以改善。(The invention discloses an AlGaN/GaN HEMT device with a local groove structure, which comprises a substrate, a buffer layer, a barrier layer and a passivation layer which are sequentially arranged from bottom to top, wherein the upper surface of the barrier layer and the left and right ends of the passivation layer are respectively provided with a source electrode and a drain electrode, and the upper surface of the barrier layer and the middle part of the passivation layer are provided with a grid electrode; the barrier layer is provided with a groove structure. The buffer layer is composed of GaN with a thickness of 2 μm and is doped with the GaN with a doping concentration of 1 × 10 15 cm ‑3 . The barrier layer is composed of AlGaN with a thickness of 0.02 μm and doped with dopant at a concentration of 1 × 10 17 cm ‑3 . The passivation layer is made of Si with the thickness of 0.05 mu m 3 N 4 And (4) forming. The lengths of the gate, source and drain are all 0.5 μm. The groove structure is made of Si with the thickness of 50nm 3 N 4 The length L of the composition is 1.0 μm, and the height H of the composition is 0.010 μm, so that the current variation is reducedSmall, current collapse is improved.)

1. The AlGaN/GaN HEMT device with the local groove structure is characterized by comprising a substrate (1), a buffer layer (2), a barrier layer (3) and a passivation layer (4) which are sequentially arranged from bottom to top, wherein a source electrode (6) and a drain electrode (7) are respectively arranged on the upper surface of the barrier layer (3) and positioned at the left end and the right end of the passivation layer (4), and a grid electrode (5) is arranged on the upper surface of the barrier layer (3) and positioned in the middle of the passivation layer (4); and a groove structure (8) is arranged on the barrier layer (3) and between the grid electrode (5) and the drain electrode (7).

2. The AlGaN/GaN HEMT device according to claim 1, wherein the buffer layer (2) is composed of GaN with a thickness of 2 μm and is doped with GaN with a concentration of 1 × 10¹⁵cm^-3。

3. The AlGaN/GaN HEMT device according to claim 1, wherein the barrier layer (3) is composed of AlGaN with a thickness of 0.02 μm and is doped with dopant with a concentration of 1 × 10¹⁷cm^-3。

4. The AlGaN/GaN HEMT device of a local groove structure according to claim 1, wherein the passivation layer (4) is made of Si with a thickness of 0.05 μm₃N₄And (4) forming.

5. The AlGaN/GaN HEMT device according to claim 1, wherein the gate (5), the source (6) and the drain (7) are all 0.5 μm in length.

6. The AlGaN/GaN HEMT device according to claim 5, wherein the gate-source distance between the gate (5) and the source (6) is 1.0 μm, and the gate-drain distance between the gate (5) and the drain (7) is 2.0 μm.

7. The AlGaN/GaN HEMT device with local groove structure according to claim 1, wherein the groove structure (8) is made of Si with a thickness of 50nm₃N₄Composition, length L1.0 μm, height H0.010 μm.

Technical Field

The invention belongs to the technical field of high electron mobility transistors, and relates to an AlGaN/GaNHEMT device with a local groove structure.

Background

Among various electronic materials and device technologies, GaN materials have excellent material characteristics such as a wide bandgap, High Electron mobility, High saturation velocity, and High breakdown electric field, and GaN High Electron Mobility Transistors (HEMTs) have made great progress in the High-frequency, High-voltage, and High-temperature field. Although GaN HEMT devices exhibit very superior performance, problems in terms of stability and reliability, etc., have limited the wide application of GaN-based devices, in which current collapse due to the trap effect has a severe influence on device performance. The cause of the current collapse effect is considered to be two factors: one is that the surface trap captures electrons in the working process of the device, and forms a certain electric potential on the surface to influence a depletion layer in a channel, thereby causing the reduction of drain current, namely the so-called 'virtual gate' effect; another factor is due to channel hot electron trapping by buffer layer traps.

The influence of the surface trap can be effectively reduced by adopting a surface passivation technology or a field plate structure, and the influence of the buffer layer trap, especially the buffer layer deep level trap on the current collapse can not be well solved, because the trap can inhibit the buffer layer leakage current and the short channel effect, which are necessary for the normal operation of the device. Therefore, further studying the influence mechanism of the buffer layer trap on the current collapse, it is an urgent problem to propose a method for improving the current collapse effect.

Disclosure of Invention

The invention aims to provide an AlGaN/GaN HEMT device with a local groove structure, which solves the problem that the current collapse effect is easily caused by a high peak electric field at the drain side of a grid edge of the AlGaN/GaN HEMT device in the prior art.

The technical scheme adopted by the invention is that the AlGaN/GaN HEMT device with the local groove structure comprises a substrate, a buffer layer, a barrier layer and a passivation layer which are sequentially arranged from bottom to top, wherein a source electrode and a drain electrode are respectively arranged on the upper surface of the barrier layer and positioned at the left end and the right end of the passivation layer, and a grid electrode is arranged on the upper surface of the barrier layer and positioned in the middle of the passivation layer; a groove structure is arranged on the barrier layer and between the grid electrode and the drain electrode.

The invention is also characterized in that:

the buffer layer is composed of GaN with a thickness of 2 μm and is doped with the GaN with a doping concentration of 1 × 10¹⁵cm^-3。

The barrier layer is composed of AlGaN with a thickness of 0.02 μm and doped with dopant at a concentration of 1 × 10¹⁷cm^-3。

The passivation layer is made of Si with the thickness of 0.05 mu m₃N₄And (4) forming.

The lengths of the gate, source and drain are all 0.5 μm.

The gate-source distance between the gate and the source was 1.0 μm, and the gate-drain distance between the gate and the drain was 2.0 μm.

The groove structure is made of Si with the thickness of 50nm₃N₄Composition, length L1.0 μm, height H0.010 μm.

The invention has the beneficial effects that: by introducing the local groove structure into the barrier layer of the traditional AlGaN/GaN HEMT device, the electric field peak value of the grid edge drain side of the AlGaN/GaN HEMT device is reduced, meanwhile, the electric field distribution expands towards the drain direction, the electric field distribution is more uniform, and therefore the current variation of the local groove structure of the barrier layer is reduced, and the current collapse is effectively improved.

Drawings

FIG. 1(a) is a schematic structural view of an AlGaN/GaN HEMT device with a partial recess structure according to the present invention;

FIG. 1(b) is a schematic structural view of a conventional AlGaN/GaN HEMT device;

FIG. 2 is a voltage bias diagram under double pulses for an AlGaN/GaN HEMT device with a local groove structure according to the present invention;

FIG. 3 is a graph of current collapse effect under double pulse for a conventional AlGaN/GaN HEMT device;

FIG. 4 shows a conventional AlGaN/GaN HEMT device at t ═ 1 × 10^-6s、t＝1×10^-3The state diagram of the trap occupied by electrons at three time points of s and t being 0.1 s;

FIG. 5 shows a conventional AlGaN/GaN HEMT device at t ═ 0.5 × 10^-7s、t＝1.05×10^-7s、t＝1.1×10^-7s and t ═ 1 × 10^-6s a concentration distribution state diagram of the trap occupied by the electrons at four time points;

FIG. 6 shows a conventional AlGaN/GaN HEMT device at t ═ 0.5 × 10^-7s、t＝1.05×10^-7s、t＝1.1×10^{- 7}s、t＝1×10^-6s、t＝1×10^-3The variation situation of the peak value of the grid edge drain side electric field at six moments when s and t are 0.1 s;

FIG. 7 is a diagram comparing the channel electric field distributions of an AlGaN/GaN HEMT device of a local groove structure of the present invention with that of a conventional AlGaN/GaN HEMT device;

FIG. 8 is a graph comparing the current collapse effect of an AlGaN/GaN HEMT device with a local groove structure of the present invention with that of a conventional AlGaN/GaN HEMT device;

FIG. 9 shows an AlGaN/GaN HEMT device with a local groove structure according to the present invention and a conventional AlGaN/GaN HEMT device at t ═ 1 × 10^-6s、t＝1×10^-3And (3) comparing the channel electric field distribution at the time when s and t are 0.1 s.

In the figure, 1 is a substrate, 2 is a buffer layer, 3 is a barrier layer, 4 is a passivation layer, 5 is a grid electrode, 6 is a source electrode, 7 is a drain electrode, and 8 is a groove structure.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention relates to an AlGaN/GaN HEMT device with a local groove structure, which comprises a substrate 1, a buffer layer 2, a barrier layer 3 and a passivation layer 4 which are sequentially arranged from bottom to top, wherein the upper surface of the barrier layer 3 and the left and right ends of the passivation layer 4 are respectively provided with a source electrode 6 and a drain electrode 7, and the upper surface of the barrier layer 3 and the middle part of the passivation layer 4 are provided with a grid electrode 5; a groove structure 8 is provided on the barrier layer 3 between the gate 5 and the drain 7. The structure of the conventional AlGaN/GaN HEMT device is shown in fig. 1(b), and comprises a substrate 1, a buffer layer 2, a barrier layer 3 and a passivation layer 4 from bottom to top.

The buffer layer 2 is made of GaN with a thickness of 2 μm, and is doped with GaN at a doping concentration of 1 × 10¹⁵cm^-3。

The barrier layer 3 is composed of AlGaN having a thickness of 0.02 μm and doped with a dopant concentration of 1 × 10¹⁷cm^-3。

The passivation layer 4 is made of Si with a thickness of 0.05 μm₃N₄And (4) forming.

The gate 5, source 6 and drain 7 are all 0.5 μm in length.

The gate-source distance between the gate 5 and the source 6 is 1.0 μm and the gate-drain distance between the gate 5 and the drain 7 is 2.0 μm.

The groove structure 8 is made of Si with a thickness of 50nm₃N₄Composition, length L1.0 μm, height H0.010 μm.

The current collapse effect of the device is researched by adopting a double-pulse technology, the pulse waveform and related parameter settings are shown in figure 2, and the static bias (V) is_gQ，V_dQ) Is (-5V, 20V), the bias (V) is tested_g，V_d) Is (0V, 5V).

Fig. 3 shows the current collapse curve of the conventional AlGaN/GaN HEMT device, as can be seen from fig. 3, where t is 1.1 × 10^-7s, the device enters the test bias phase, but the output current does not reach a stable value directly, but remains at an initial value for a period of time (from t ═ 1.1 × 10)^-7s to t ═ 10^-4s) is gradually increased to a stable value, and the result shown in fig. 3 shows that the AlGaN/GaN HEMT device has a significant current collapse effect. In order to deeply analyze the mechanism of the current collapse generation, the test bias stage is divided into three parts, wherein t is 1.1 multiplied by 10^-7s to 10^-4s output current is basically kept unchanged, which is called as a current keeping stage; t 10^-4s to 2X 10^-2The s current increases with time, called the current rise phase; t 2 × 10^-2After s, the output current remains almost unchanged, referred to as the current stabilization phase. Taking t as 1 × 10 in three stages of current holding, rising and stabilizing^-6s、t＝1×10^-3Fig. 4 shows how the traps are occupied by electrons at three time points of s and t being 0.1s, and it can be seen that the probability of the traps of the buffer layer being occupied by electrons gradually decreases with the increase of time, which corresponds to the process of releasing electrons by the traps.

FIG. 5 shows that t is 0.5 × 10^-7s、t＝1.05×10^-7s、t＝1.1×10^-7s and t ═ 1 × 10^-6And (4) probability distribution conditions of the devices corresponding to the s four time points, wherein the buffer layer traps are occupied by electrons near the edge of the grid electrode close to the drain electrode. As shown in fig. 5, prior to the test bias phase, the device is in the process of trapping electrons in buffer layer traps. The concentration of trapped electrons in the trap at the very beginning of the test bias phaseTo a maximum. According to the process of releasing electrons by the traps in the test bias stage, the electrons released by the traps in the buffer layer come from the static bias stage and the electrons trapped in the traps in the transition state from the static bias stage to the test bias stage in the vicinity of the edge of the grid close to the drain in the test bias stage.

In fig. 6, t is 0.5 × 10^-7s、t＝1.05×10^-7s、t＝1.1×10^-7s and t ═ 1 × 10^-6And s four time points of the peak condition of the electric field at the edge of the grid and the drain side. As shown in fig. 6, the electric field peak gradually decreases with time, and becomes 1.0 × 10 at t^-7Before s, the device is in a static bias stage, the peak value of an electric field is the largest, and channel electrons on the drain side of the gate edge jump into the buffer layer under the action of the high electric field and are captured by an acceptor trap in the buffer layer. Due to the depletion of the channel under the gate, channel electrons on the drain side at the edge of the gate cannot be compensated after being trapped by the trap, resulting in depletion of channel electrons there. And as time goes on, the device enters a transition state between static bias and test bias, the device is in a semi-conduction state at the moment, electrons are generated in a channel below the grid electrode and are compensated towards the channel on the drain side of the edge of the grid electrode, but because the potential difference between the grid electrode and the drain electrode is still large, the electrons at the position can continuously jump and are captured by a trap in the buffer layer under the action of the electric field peak value. In the test bias stage, a channel under a gate is completely opened, the potential difference between gates and a drain is small, the peak value of an electric field is too small to enable channel electrons to jump, in order to maintain balance, the trap of the buffer layer starts to release electrons, so that the channel electron concentration on the drain side of the edge of the gate is gradually increased, the distribution of the electron concentration in the channel tends to be uniform, the distribution of the electric field of the channel also tends to be uniform, and finally the electron concentration reaches a stable state. Since the magnitude of the output current is related to the 2DEG density in the channel, the output current also changes with time, forming a current collapse effect under transient conditions.

The electric field peak value of the grid edge drain side is a key factor causing the current collapse effect, and the provided local groove structure 8 of the AlGaN/GaN HEMT barrier layer 3 can remarkably reduce the electric field peak value of the grid edge drain side and improve the current collapse effect in the working process of a device.

FIG. 7 is a diagram showing the distribution of the electric field intensity of the lateral channel when the partial groove structure of the barrier layer and the conventional structure just enter the bias stage of testing. As shown in fig. 7, compared with the conventional structure, the peak value of the electric field at the drain side of the gate edge of the groove structure 8 is lower than that of the conventional structure, and the electric field distribution is expanded towards the drain direction and is more uniform.

FIG. 8 is a time-dependent change curve of the partial groove structure of the AlGaN/GaN HEMT barrier layer and the output current of the conventional device when the length L of the groove is 1.0 μm and the height H is 0.010 μm. As shown in fig. 8, compared with the conventional structure, the current collapse amount of the groove structure 8 is reduced from 13.59% to 10.56%, and the performance is improved by 22.30%.

To further analyze the effectiveness of the groove structure in improving the current collapse effect, fig. 9 shows that t is 1 × 10^-6s、t＝1×10^-3And s and t are 0.1s, and the electric field distribution in the channels of the two device structures at three typical times. As shown in fig. 9, t is 1 × 10^-6In the time from s to t being 0.1s, the electric field peak value variation of the barrier layer local groove structure is far smaller than that of the traditional AlGaN/GaN HEMT device. The small variation of the electric field is due to the small variation of the electron concentration, which leads to the reduced variation of the current of the partial groove structure of the barrier layer in fig. 8, and the current collapse is improved.

The AlGaN/GaN HEMT device with the local groove structure has the beneficial effects that: according to the invention, the groove structure 8 is introduced into the edge of the grid 5 to reduce the electric field peak value at the drain side of the edge of the grid, so that the electric field distribution is expanded towards the drain direction and is more uniform, the current variation of the local groove structure 8 on the barrier layer 3 is reduced, and the current collapse is improved.