阅读说明：本技术 一种高In组分台面型InGaAs焦平面探测器及其制备方法 (Mesa InGaAs focal plane detector with high In component and preparation method thereof ) 是由 顾溢 孙夺 刘大福 李雪 于 2020-09-30 设计创作，主要内容包括：本发明公开了一种高In组分台面型InGaAs焦平面探测器及其制备方法,其包括一探测器主体层、钝化膜层和欧姆接触层；探测器主体层由下往上依次包括InP衬底、InP缓冲层、n型In_yAl_(1-y)As缓冲层、n型In_xGa_(1-x)As吸收层、p型In_xAl_(1-x)As耗尽层和p型In_xGa_(1-x)As接触层；探测器主体层表面覆盖有钝化膜层；p型In_xGa_(1-x)As接触层分为像元区和像元分隔区,像元分隔区的深度等于p型In_xGa_(1-x)As接触层的厚度；p型In_xAl_(1-)_xAs耗尽层的厚度为20-70nm；0.53≤x＜1；0.52≤y≤x。本发明的探测器结构,可以大幅降低焦平面探测器的总体暗电流。(The invention discloses a mesa InGaAs focal plane detector with high In component and a preparation method thereof, comprising a detector main body layer, a passivation film layer and an ohmic contact layer; the detector main body layer sequentially comprises an InP substrate, an InP buffer layer and n-type In from bottom to top y Al 1‑y As buffer layer and n-type In x Ga 1‑x As absorption layer, p-type In x Al 1‑x As depletion layer and p-type In x Ga 1‑x An As contact layer; a passivation film layer covers the surface of the detector main body layer; p-type In x Ga 1‑x The As contact layer is divided into a pixel region and a pixel separation region, and the depth of the pixel separation region is equal to that of the p-type In x Ga 1‑x Of As contact layersThickness; p-type In x Al 1‑ x The thickness of the As depletion layer is 20-70 nm; x is more than or equal to 0.53 and less than 1; y is more than or equal to 0.52 and less than or equal to x. The detector structure of the invention can greatly reduce the total dark current of the focal plane detector.)

1. A mesa InGaAs focal plane detector with high In component is characterized by comprising a detector main body layer, a passivation film layer and an ohmic contact layer;

the detector main body layer sequentially comprises an InP substrate, an InP buffer layer and n-type In from bottom to top_yAl_1-yAs buffer layer and n-type In_xGa_1-xAs absorption layer, p-type In_xAl_1-xAs depletion layer and p-type In_xGa_1-xAn As contact layer;

the surface of the detector main body layer is covered with the passivation film layer;

the p-type In_xGa_1-xThe As contact layer is divided into a pixel region and a pixel separation region, and the depth of the pixel separation region is equal to that of the p-type In_xGa_1-xThickness of the As contact layer;

the p-type In_xAl_1-xThe thickness of the As depletion layer is 20-70 nm;

0.53≤x＜1；0.52≤y≤x。

2. the high In composition mesa type InGaAs focal plane detector of claim 1, wherein the thickness of the InP substrate is In the range of 350-650 μm, such as 620 μm;

and/or the InP buffer layer has a thickness in the range of 0.2-1 μm, for example 500nm or 200 nm;

and/or, the n-type In_yAl_1-yThe thickness of the As buffer layer is in the range of 1-3 μm, such As 2 μm or 2.5 μm;

and/or, the n-type In_yAl_1-yThe doping source of the As buffer layer is Si or S, such As Si;

and/or, the n-type In_xGa_1-xThe As absorbing layer has a thickness in the range of 1-3 μm, for example 1.5 μm or 2 μm;

and/or, the n-type In_xGa_1-xThe doping source of the As absorption layer is Si or S, such As Si;

and/or, the p-type In_xAl_1-xThe doping source of the As depletion layer is Be or Zn;

and/or, the p-type In_xGa_1-xThe thickness range of the As contact layer is 200-500nm, such As 300 nm;

and/or, the p-type In_xGa_1-xThe doping source of the As contact layer is Be or Zn.

3. The high In composition mesa type InGaAs focal plane detector of claim 2, wherein the n-type In is_yAl_1-yThe carrier concentration in the As buffer layer is 1X 10¹⁸cm^-3-5×10¹⁸cm^-3E.g. 1X 10¹⁸Or 3X 10¹⁸cm^-3；

And/or, the n-type In_xGa_1-xCarrier concentration in As absorption layer is 1X 10¹⁴cm^-3-5×10¹⁶cm^-3E.g. 2 x 10¹⁶cm^-3Or 5X 10¹⁵cm^-3；

And/or, the p-type In_xAl_1-xCarrier concentration in As depletion layer is 1X 10¹⁷cm^-3～1×10¹⁸cm^-3E.g. 2 x 10¹⁷cm^-3Or 1X 10¹⁸cm^-3；

And/or, the p-type In_xGa_1-xAs contact layer having a carrier concentration of 1X 10¹⁸cm^-3～5×10¹⁸cm^-3E.g. 3X 10¹⁸cm^-3Or 5X 10¹⁸cm^-3。

4. The high In composition mesa type InGaAs focal plane detector of claim 1, wherein the bottom surface of the pixel isolation region is the p-type In focal plane detector_xAl_1-xAn upper surface of the As depletion layer;

and/or the width of the picture element separation area is in the range of 1-5 μm, such as 2 μm;

and/or the size of the pixel area is 10-300 mu m x 10-300 mu m.

5. The high In composition mesa type InGaAs focal plane detector of claim 1, wherein the material of the passivation film layer is Si₃N₄Or SiO₂；

And/or the thickness of the passivation film layer is 200-500nm, such as 300 nm;

and/or the thickness of the ohmic contact layer is 100-500 nm.

6. The high In composition mesa type InGaAs focal plane detector of claim 1, wherein the ohmic contact layer comprises a p-type ohmic contact layer and an n-type ohmic contact layer;

the p-type ohmic contact layer penetrates through the passivation film layer and is arranged on the surface of the pixel region or embedded in the pixel region;

and/or the size of the p-type ohmic contact layer is 5-30 [ mu ] m multiplied by 5-30 [ mu ] m;

and/or the n-type ohmic contact layer penetrates through the passivation film layer and is arranged on the n-type In_xGa_1-xAs absorption layer or the n-type In_yAl_1-yAn As buffer layer on the surface or embedded In the n-type In_xGa_1-xAs absorption layer or the n-type In_yAl_1-yAn As buffer layer;

and/or the size of the n-type ohmic contact layer is larger than 50 microns multiplied by 10 microns and smaller than the size of the detector.

7. The high In composition mesa type InGaAs focal plane probe of claim 6The sensor is characterized In that the n-type ohmic contact layer penetrates through the passivation film layer and is arranged on the n-type In_yAl_1-yThe surface of the As buffer layer.

8. The method for preparing the high In composition mesa type InGaAs focal plane detector as claimed In any one of claims 1 to 7, comprising:

(1) sequentially growing the InP buffer layer and the n-type In on the InP substrate_yAl_1-yAs buffer layer and n-type In_xGa_1-xAs absorption layer and p-type In_xAl_1-xAs depletion layer, the p-type In_xGa_1-xAn As contact layer constituting the probe body layer;

(2) in the p-type In_xGa_1-xThe pixel region and the pixel separation region are formed on the As contact layer;

(3) and growing the passivation film layer and the ohmic contact layer on the detector body layer.

9. The method according to claim 8, wherein in the step (1), the growth method is a molecular beam epitaxy method;

and/or, in the step (2), the method for forming the pixel area and the pixel separation area is dry etching or wet etching;

and/or in the step (3), the method for growing the passivation film layer is a magnetron sputtering method or a chemical vapor deposition method;

and/or in the step (3), the method for growing the ohmic contact layer is an electron beam evaporation method or a magnetron sputtering method.

10. The method of claim 9, wherein the wet etching has a rate of 0.5-1 μm/min, such as 0.6 μm/min;

alternatively, the dry etching is performed with Cl₂And CH₄As an etching gas, etching at an etching rate of about 0.5 to 1.5 μm/min;

and/or, in the step (1), the growth rate is 0.5-1.5 μm/h.

Technical Field

The invention belongs to the field of semiconductor optoelectronic devices, and particularly relates to a mesa type InGaAs focal plane detector with high In component and a preparation method thereof.

Background

Short wave infrared (1-3 micron) wave band has many important applications in the fields of communication, remote sensing, imaging and the like. There are many semiconductor detectors in this band, among which the detectors made of III-V InGaAs material can work at higher temperature, have higher response speed, and quantum efficiency can exceed 70%, so it is a main choice in this band. The InGaAs material has direct band gap In all components, is lattice matched with the InP substrate when the In component is 0.53, has the forbidden bandwidth of 0.74eV at room temperature, is used as an absorption layer to manufacture a detector with the cut-off wavelength of about 1.7 microns, and can cover the wavelengths of 1.3 and 1.55 microns of long-wave optical fiber communication, so that In is adopted_0.53Ga_0.47Semiconductor detectors made of As materials are widely applied to the field of optical communication.

In addition, in the field of remote sensing and sensing, many applications require detectors with cut-off wavelengths greater than 1.7 microns; for example, the characteristic absorption line wavelengths of substances such as ice clouds, cirrus clouds, minerals, vegetation and the like are all located in the range of 2.1-2.5 microns, so that the spatial remote sensing of the wave band can obtain abundant information, and the cutoff wavelength of a detector is required to be larger than 1.7 microns; as another example, coherent doppler wind radars, which also require 2 micron band detectors, can achieve atmospheric wind field results with higher speed accuracy and range resolution than conventional operation at 10 micron and 1.06 micron wavelengths.

Albeit by increasing In_xGa_1-xThe In component x In the As absorption layer material can reduce the forbidden bandwidth of the InGaAs material, thereby increasing the cut-off wavelength of the InGaAs detector, for example, when the In component reaches 0.8, the cut-off wavelength of the InGaAs detector can reach about 2.4 microns; however, after the In component was increased,because lattice mismatch between the InGaAs absorption layer and the InP substrate and dislocations exist in the materials, the buffer layer is generally grown on the InP substrate and the InGaAs absorption layer is then grown. The InAlAs buffer layer is one of the main buffer layers, and after the buffer layer is adopted, the dislocation in the InGaAs absorbing layer material is reduced, but still far more than the lattice matched material.

For the InGaAs focal plane detector with high In component, the p-type diffusion process control of the planar structure has difficulty, so the mesa structure is often adopted. The p-type doping layer is formed by adopting in-situ growth, a mesa structure is formed by etching to separate adjacent pixels of a focal plane, and the dark current of a depletion region near a pn junction on the side wall of the mesa is one of main sources of the dark current of the mesa device. Currently, device dark current is a core bottleneck limiting the performance of high In composition InGaAs devices for a wide variety of applications. Therefore, it is highly desirable to reduce the dark current of mesa-type InGaAs detectors with high In composition.

Disclosure of Invention

The invention aims to solve the technical problem that the dark current In the mesa InGaAs focal plane detector with high In component In the prior art is higher (the dark current density at room temperature is generally 1 multiplied by 10)^-5～5×10^-4A/cm²) The dark current density of the detector at room temperature can be reduced to 1/2-2/3 of the conventional dark current density.

In the art, the conventional depletion layer is so thin (on the order of a few nanometers) that it is difficult to retain the depletion layer during etching, thereby resulting in a large dark current. In the experimental process, the inventor finds that if the thickness of the depletion layer is increased, although the dark current can be reduced to a certain extent, the contact effect of the contact layer and the p-type ohmic contact metal becomes poor, so that the responsivity of the focal plane detector is low, and even the function of the detector is abnormal, so how to reduce the dark current is an urgent problem to be solved in the art on the premise of ensuring that the contact effect of the contact layer and the p-type ohmic contact metal is good. The inventor of the invention discovers through creative work that the problem of poor contact effect of a contact layer and p-type ohmic contact metal can be solved and the density of dark current can be remarkably reduced by controlling the thickness of a depletion layer within the range of 20-70nm, the arrangement position of a pixel separation region and other necessary technical characteristics.

The invention solves the technical problems by the following scheme:

a mesa InGaAs focal plane detector with high In component comprises a detector main body layer, a passivation film layer and an ohmic contact layer;

the detector main body layer sequentially comprises an InP substrate, an InP buffer layer and n-type In from bottom to top_yAl_1-yAs buffer layer and n-type In_xGa_1-xAs absorption layer, p-type In_xAl_1-xAs depletion layer and p-type In_xGa_1-xAn As contact layer;

the surface of the detector main body layer is covered with the passivation film layer;

the p-type In_xGa_1-xThe As contact layer is divided into a pixel region and a pixel separation region, and the depth of the pixel separation region is equal to that of the p-type In_xGa_1-xThickness of the As contact layer;

the p-type In_xAl_1-xThe thickness of the As depletion layer is 20-70 nm;

0.53≤x＜1；0.52≤y≤x。

in the present invention, the thickness of the InP substrate can be in the range of conventional art, preferably 350-650 μm, such as 620 μm. The InP substrate may be doped or undoped with other elements as generally desired.

In the present invention, the thickness of the InP buffer layer may be in the range of conventional art, preferably 0.2-1 μm, such as 500nm or 200 nm. The InP buffer layer may be doped or undoped, e.g., undoped, as desired.

In the present invention, the n-type In_yAl_1-yThe thickness of the As buffer layer may be in the range conventional in the art, and is preferably 1-3 μm, for example 2 μm or 2.5 μm.

In the present invention, the n-type In_yAl_1-yAs bufferThe dopant source for the layer may be conventional in the art, preferably Si or S, e.g. Si. Wherein the n-type In_yAl_1-yThe carrier concentration in the As buffer layer may be a concentration conventional in the art, and is preferably 1X 10¹⁸cm^-3-5×10¹⁸cm^-3E.g. 1X 10¹⁸Or 3X 10¹⁸cm^-3。

In the present invention, the n-type In_xGa_1-xThe thickness of the As absorbing layer may be in the range conventional in the art, preferably 1-3 μm, for example 1.5 μm or 2 μm.

In the present invention, the n-type In_xGa_1-xThe dopant source for the As absorber layer may be conventional in the art, and is preferably Si or S, such As Si. Wherein the n-type In_xGa_1-xThe carrier concentration in the As absorption layer may be a concentration conventional in the art, and is preferably 1X 10¹⁴cm^-3-5×10¹⁶cm^-3E.g. 2 x 10¹⁶cm^-3Or 5X 10¹⁵cm^-3。

In the present invention, the p-type In_xAl_1-xThe dopant source for the As depletion layer may Be conventional in the art, preferably Be or Zn. Wherein the p-type In_xAl_1-xThe carrier concentration in the As depletion layer is preferably 1X 10¹⁷cm^-3～1×10¹⁸cm^-3E.g. 2 x 10¹⁷cm^-3Or 1X 10¹⁸cm^-3。

As known to those skilled In the art, In general, the p-type In_xAl_1-xThe As depletion layer is fully depleted during device operation.

In the present invention, the p-type In_xGa_1-xThe thickness of the As contact layer may be in the range conventional in the art, preferably 200-500nm, such As 300 nm. The p-type In_xGa_1-xThe dopant source for the As contact layer may Be conventional in the art, and is preferably Be or Zn. Wherein the p-type In_xGa_1-xThe carrier concentration of the As contact layer can be conventional in the art, and is preferably 1X 10¹⁸cm^-3～5×10¹⁸cm^-3E.g. 3X 10¹⁸cm^-3Or 5X 10¹⁸cm^-3。

In the present invention, the p-type In is known to those skilled In the art_xGa_1-xThe As contact layer is etched to form the pixel region and the pixel separation region, and the etched part forms a groove which is the pixel separation region; the part which is not etched is the image element area.

The depth of the pixel separation region is the depth of the groove and is equal to the p-type In_xGa_1-xThe thickness of the As contact layer, that is, the thickness of the picture element region. The bottom surface of the pixel separation region is the p-type In_xAl_1-xThe upper surface of the As depletion layer.

In the invention, the number of the pixel separation areas is related to the pixel scale of the focal plane detector, and generally, the pixel separation area is arranged between every two adjacent pixels. The width of the pixel separation region, which is the perpendicular distance between two adjacent pixel regions, may range from 1 to 5 μm, for example 2 μm.

In the invention, the pixel area can have the size of length (10-300) mu m multiplied by width (10-300) mu m.

In the present invention, the material of the passivation film layer may be conventional in the art, such as Si₃N₄Or SiO₂. The thickness of the passivation film layer may be conventional in the art, and is preferably 200-500nm, such as 300 nm.

In the present invention, the thickness of the ohmic contact layer may be a thickness conventional in the art, and is preferably 100-500 nm.

In the present invention, the ohmic contact layer generally includes a p-type ohmic contact layer and an n-type ohmic contact layer. Wherein, the metal of the p-type ohmic contact layer can be conventional in the art, for example, the Ti/Pt/Au three-layer metal can be a p-type metal layer. The metal of the n-type ohmic contact layer may be conventional in the art, for example, the Cr/Au two-layer metal may be an n-type metal layer.

The p-type ohmic contact layer generally penetrates through the passivation film layer and is arranged on the surface of the pixel region or embedded in the pixel region. Generally, each pixel region corresponds to one p-type ohmic contact layer.

Wherein, the size of the p-type ohmic contact layer can be 5-30 μm long by 5-30 μm wide.

Wherein the n-type ohmic contact layer generally penetrates through the passivation film layer and is disposed on the n-type In_xGa_1-xAs absorption layer or the n-type In_yAl_1-yAn As buffer layer on the surface or embedded In the n-type In_xGa_1-xAs absorption layer or the n-type In_yAl_1-yAn As buffer layer.

The n-type ohmic contact layer preferably penetrates through the passivation film layer and is disposed on the n-type In_yAl_1-yThe surface of the As buffer layer.

The size of the n-type ohmic contact layer can be larger than 50 μm in length by 10 μm in width and smaller than the size of the array of the detector.

In the present invention, x and y represent the proportion of In atoms to the sum of In and Ga atoms and the proportion of In atoms to the sum of In and Al atoms In the material, respectively.

In the invention, the InP substrate, the InP buffer layer and the n-type In_yAl_1-yAs buffer layer and n-type In_xGa_1-xAs absorption layer and p-type In_xAl_1-xAs depletion layer and said p-type In_xGa_1-xThe area of the As contact layer can be conventional in the art, and the area of each layer can be set according to the size of the detector being fabricated.

A preparation method of the mesa InGaAs focal plane detector with high In component comprises the following steps:

(1) sequentially growing the InP buffer layer and the n-type In on the InP substrate_yAl_1-yAs buffer layer and n-type In_xGa_1-xAs absorption layer and p-type In_xAl_1-xAs depletion layer, the p-type In_xGa_1-xAn As contact layer constituting the probe body layer;

(2) in the p-type In_xGa_1-xThe pixel region and the pixel separation region are formed on the As contact layer;

(3) and growing the passivation film layer and the ohmic contact layer on the detector body layer.

In step (1), the growth method may be an epitaxial material growth method conventional in the art, such as molecular beam epitaxy. The thickness of each layer in the detector body layer can be ensured by controlling the carrier concentration, and the carrier concentration can be controlled by controlling the temperature of the doping source.

Wherein the growth rate may be 0.5-1.5 μm/h.

In step (2), the method for forming the pixel region and the pixel separation region may be a method conventional in the art, such as wet etching, dry etching, and the like. Etching off the p-type In corresponding to the pixel separation region on the focal plane_xGa_1-xAs contact layer while retaining the p-type In_xAl_1-xThe original thickness of the As depletion layer, shallow isolation grooves among the pixels are pixel separation areas.

The wet etching is generally performed by using hydrobromic acid, and the wet etching rate may be 0.5-1 μm/min, for example, 0.6 μm/min. The dry etching is generally referred to as an inductively coupled plasma etching method. The inductively coupled plasma etching method generally refers to Cl₂And CH₄As an etching gas, dry etching was performed at an etching rate of about 0.5 to 1.5 μm/min.

Wherein, In the process of forming the pixel region and the pixel separation region, the depth of the pixel separation region is determined by a step profiler to confirm that the depth of the pixel separation region is equal to the p-type In_xGa_1-xThickness of the As contact layer.

In the step (3), the method for growing the passivation film layer may be a conventional growing method in the art, such as a magnetron sputtering method or a chemical vapor deposition method.

In the step (3), the method for growing the ohmic contact layer may be a growth method conventional in the art, such as an electron beam evaporation method or a magnetron sputtering method. The growth rate can be controlled according to the power and temperature parameters conventional in the art.

When the ohmic contact layer is grown, the corresponding passivation film layer is generally removed at the corresponding position of the detector body layer through photoetching and etching, and then the ohmic contact layer is grown.

In the present invention, the InP substrate, high-purity metals In, Ga, Al, and high-purity As, P, etc. may be conventional In the art, for example, the InP substrate may be purchased from AXT, Inpact, leader, etc.; the high-purity metals In, Ga and Al can be purchased from PPM, UMC, lead and other companies; high purity As and P are available from lead, EME, etc.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows:

the InGaAs mesa focal plane detector structure with high In component provided by the invention controls p-type In_xAl_1-xThe thickness of the As depletion layer and the depth of the pixel separation region eliminate the side wall of the table top of the InGaAs absorption layer of the focal plane photosensitive region, so that the surface dark current caused by the thickness can be greatly inhibited, and the total dark current of the focal plane detector is reduced: can be reduced to 1/2-2/3 of the conventional dark current density.

Drawings

FIG. 1 is a schematic view of the structure of an In0.74Ga0.26As mesa type focal plane detector of embodiment 1;

FIG. 2 is a schematic view of the structure of an In0.8Ga0.2As mesa type focal plane detector of example 2;

fig. 3 is a schematic plan view of the high In composition InGaAs mesa focal plane detector of the present invention.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

In the following examples: the dark current testing method adopts a semiconductor parameter analyzer for testing, and the apparatus is B1500A of Agilent company;

InP substrate, high-purity metals of In, Ga and Al, and high-purity As and P are purchased from Guangdong leading Dilute stock Co Ltd;

molecular beam epitaxy is referred to as "wavelegth extended 2.4 μm heterojunction InGaAs photomodides with InAlAs cap and linear graded fillers available for born front and back pumping, Y.G.Zhang, Y.Gu.et.al, Infrared Phys. & Technol.51,316-321 (2008)"; the growth rate was 1 μm/h.

The chemical vapor process adopts the equipment of SI500D equipment of Sentech company;

the electron beam evaporation process adopts equipment of ULVAC company ei-5 model;

the areas of the InP substrate, buffer layer, absorber layer, depletion layer, and contact layer are all 3-inch diameter circles.

Example 1

Example 1 illustrates In according to the invention_0.74Ga_0.26In the method for manufacturing the As mesa type focal plane detector structure, the array of the focal plane detector in this embodiment is 640 rows × 512 columns, the structure is shown in fig. 3, and the main steps for manufacturing the structure are shown in fig. 1, specifically:

(1) epitaxially growing an InP buffer layer (undoped, 500nm thick) and n-type In on InP substrate (620 μm thick)_yAl_1-yAs buffer layer (doping source Si, carrier concentration 1X 10)¹⁸cm^-3Thickness 2 μm, with y gradually increasing from 0.52 to 0.74; n-type In_0.74Ga_0.26As absorption layer (doping source Si, carrier concentration 2X 10)¹⁶cm^-3Thickness 1.5 μm), p-type In_0.74Al_0.26As depletion layer (dopant source Be, carrier concentration 2X 10)¹⁷cm^-3Thickness 70nm) and p-type In_0.74Ga_0.26As contact layer (doping source Be, carrier concentration 3X 10)¹⁸cm^-3300nm in thickness);

(2) by using hydrobromic acid on p-type In_0.74Ga_0.26Wet etching is carried out on the As contact layer, the etching rate is 0.6 mu m/min, and meanwhile, the p type is keptIn_0.74Al_0.26The original thickness of the As depletion layer (i.e., without destroying the depletion layer), thereby forming the pixel region (30 μm × 30 μm) and the pixel separation region As shown in fig. 3; wherein the width of the pixel separation region is 2 μm and the depth is 300 nm.

The edge of the focal plane is etched by the same method and conditions, from p-type In_0.74Ga_0.26Etching As contact layer to n-type In_yAl_1-yThe surface of the As buffer layer is grooved to a depth equal to 1.87 μm.

(3) Using silane and ammonia gas as raw material gas, adopting chemical vapor deposition process to grow Si₃N₄Passivation film, Si₃N₄The thickness of the passivation film layer is 300 nm.

(4) And (3) removing a part of the passivation film layer on the pixel region by adopting the same etching method as the step (2) (the corresponding dimension is 8 mu m multiplied by 8 mu m of the p-type ohmic contact metal layer), and growing the p-type ohmic contact metal layer by adopting an electron beam evaporation process. The metal of the p-type ohmic contact metal layer is three layers of Ti/Pt/Au, and the thickness is 100 nm;

firstly adopting the same etching method as the step (2) to etch the n-type In_yAl_1-yAnd removing a part of passivation film layer on the surface of the As buffer layer (the corresponding size is 100 mu m multiplied by 50 mu m of the size of the n-type ohmic contact metal layer), and growing the n-type ohmic contact metal layer by adopting the same electron beam evaporation process, wherein the metal of the n-type ohmic contact metal layer is Cr/Au, and the thickness is 100 nm.

Effect data: the detector of this embodiment has a dark current density of 7 × 10 at room temperature^-6A/cm²Dark current density at 200K 8X 10^-10A/cm²(ii) a Detection rate at room temperature of 1X 10¹¹cmHz^1/2The detection rate reaches 3 multiplied by 10 under the condition of 200K¹²cmHz^1/2/W。

Example 2

Example 2 illustrates In according to the invention_0.8Ga_0.2As mesa type focal plane detector structure and its preparation method, the focal plane detector array in this implementation is 640 rows by 512 columns, its structure is shown in FIG. 3, the main steps for preparing the structureAs shown in fig. 2, specifically:

(1) epitaxially growing an InP buffer layer (undoped, 200nm thick) and n-type In on InP substrate (620 μm thick)_yAl_1-yAs buffer layer (doping source Si, carrier concentration 3X 10)¹⁸cm^-3N-type In with a thickness of 2.5 μm and a gradual increase of y from 0.52 to 0.8_0.8Ga_0.2As absorption layer (doping source Si, carrier concentration 5X 10)¹⁵cm^-3Thickness 2 μm), p-type In_0.8Al_0.2As depletion layer (doping source Zn, carrier concentration 1X 10)¹⁸cm^-3Thickness 20nm) and p-type In_0.8Ga_0.2As contact layer (doping source Zn, carrier concentration 5X 10)¹⁸cm^-3500nm in thickness);

(2) by using hydrobromic acid on p-type In_0.8Ga_0.2Wet etching is carried out on the As contact layer, the etching rate is 0.6 mu m/min, and meanwhile, p-type In is reserved_0.8Al_0.2The original thickness of the As depletion layer (i.e., without destroying the depletion layer), thereby forming the pixel region (30 μm × 30 μm) and the pixel separation region As shown in fig. 3; wherein the width of the pixel separation region is 2 μm and the depth is 500 nm.

The edge of the focal plane is etched by the same method and conditions, from p-type In_0.8Ga_0.2Etching As contact layer to n-type In_yAl_1-yThe surface of the As buffer layer is grooved to a depth equal to 2.52 μm.

(3) Using silane and ammonia gas as raw material gas, adopting chemical vapor deposition process to grow SiO₂Passivating film, SiO₂The thickness of the passivation film layer is 300 nm.

(4) And (3) removing a part of the passivation film layer on the pixel region by adopting the same etching method as the step (2) (the corresponding dimension is 8 mu m multiplied by 8 mu m of the p-type ohmic contact metal layer), and growing the p-type ohmic contact metal layer by adopting an electron beam evaporation process. The metal of the p-type ohmic contact metal layer is three layers of Ti/Pt/Au, and the thickness is 100 nm;

firstly adopting the same etching method as the step (2) to etch the n-type In_yAl_1-yA part of the passivation film layer on the surface of the As buffer layer is removed (corresponding toThe size of the n-type ohmic contact metal layer is 100 mu m multiplied by 50 mu m), the n-type ohmic contact metal layer is grown by adopting the same electron beam evaporation process, wherein the metal of the n-type ohmic contact metal layer is Cr/Au, and the thickness is 100 nm.

Effect data: the detector of this embodiment has a dark current density of 2X 10 at room temperature^-4A/cm²Dark current density at 200K 1X 10^-9A/cm². Detection rate at room temperature of 6X 10¹⁰cmHz^1/2The detection rate reaches 2 multiplied by 10 under the condition of 200K¹²cmHz^1/2/W。