CN110165012A - A kind of photodetector structure and preparation method thereof with the anti-reflection effect of arc - Google Patents

Abstract

The invention relates to a photodetector structure with arc-shaped anti-reflection effect and a preparation method thereof. The structure sequentially includes a substrate, a P-type heavily doped material layer, an N-type lightly doped material layer, an N-type transition material layer, an N-type lightly doped material layer, an N-type heavily doped material layer and N-type ohmic electrode; P-type ohmic electrode is located on the P-type heavily doped material layer outside the N-type lightly doped material layer; wherein, the N-type ohmic electrode is circular and located on the outer edge of the N-type heavily doped material layer The N-type heavily doped material layer exposed in the middle is a photosensitive area with a thickness of 0.1-1 μm, and the upper surface of the photosensitive area contains an arc structure, and the arc structure is arc, overlapping arc, or concave-convex shape. The preparation method of the invention is simple, strong in operability and low in cost, and while further enhancing the light transmittance, the light incident into the device can be distributed more uniformly, the self-heating effect of the device can be reduced, and the quantum efficiency can be improved.

Description

A photodetector structure with arc-shaped anti-reflection effect and its preparation method

technical field

The invention relates to a photodetector structure with an arc anti-reflection effect and a preparation method thereof, in particular to a preparation method of an avalanche photodetector with high responsivity, belonging to the technical field of semiconductor optoelectronic devices.

Background technique

Ultraviolet detection technology is a military-civilian dual-use photoelectric detection technology developed after infrared and laser detection technology, and ultraviolet detector is the core component of ultraviolet detection system, in fire monitoring, ultraviolet curing, ultraviolet disinfection, medical care, national defense Early warning, missile warning and other fields have very important application prospects. In recent years, solid-state ultraviolet detectors based on wide-bandgap semiconductor avalanche photodiodes (APDs) have attracted widespread international research interest, aiming to replace the bulky, expensive, and fragile photomultiplier tubes (PMTs) that are currently widely used.

Gallium Nitride (GaN) and Silicon Carbide (SiC) APDs are expected to simultaneously achieve high gain, high quantum efficiency, low dark current, low overload noise, and weak signal "visible light blind" ultraviolet due to their unique material and device performance advantages. probed semiconductor devices. Common photodetector structures include: metal-semiconductor-metal (MSM) structure, PN/PIN structure, and avalanche photodetector (APD) structure. No matter what kind of device structure is used, it is hoped to improve the responsivity of the device to increase the detection sensitivity. Based on this, researchers have done a series of research. The Chinese patent No. CN106784121A discloses a surface plasmon photodetector and a preparation method thereof, wherein the metal electrode is made into an interdigitated periodic grating, and the charge density wave of free electrons in the metal grating is used to couple with the incident electromagnetic wave, causing the charge density to fluctuate and cause collective oscillation, so that the charge density wave does not decrease The response speed of the detector is increased while the responsivity is increased; the Chinese patent No. CN107275441A discloses a preparation method of a ZnO anti-reflection film photodetector, which prepares a well-crystallized, smooth and compact photodetector by changing the parameters such as sintering temperature and holding time. , ZnO sputtering target with excellent performance, so as to improve the light transmittance of ZnO anti-reflection coating and increase the responsivity. Although the detector responsivity has been improved to a certain extent, it is at the cost of complicated process procedures and high preparation costs.

Contents of the invention

The object of the present invention is to provide a photodetector structure with arc-shaped anti-reflection effect and a preparation method thereof for the deficiencies in the current technology. This structure increases light transmittance by etching the photosensitive area at the top of the device into an arc-shaped structure. The preparation method of the invention is simple, has strong operability and low cost, and while further enhancing the light transmittance, it can also make the light distribution incident into the device more uniform, avoid a large amount of photogenerated carriers from accumulating, and reduce the self-heating effect of the device , to improve quantum efficiency.

The technical solution adopted by the present invention to solve the technical problem is:

A photodetector structure with an arc-shaped anti-reflection effect, the structure sequentially includes a substrate, a P-type heavily doped material layer, an N-type lightly doped material layer, an N-type transition material layer, and an N-type Lightly doped material layer, N-type heavily doped material layer and N-type ohmic electrode; P-type ohmic electrode is located on the P-type heavily doped material layer outside the N-type lightly doped material layer; wherein, the N-type ohmic electrode is a circle Annular, located on the outer edge of the N-type heavily doped material layer, the N-type heavily doped material layer exposed in the middle is a photosensitive area with a thickness of 0.1-1 μm, and the upper surface of the photosensitive area contains an arc structure, so The arc-shaped structure is arc-shaped, overlapping arc-shaped or concave-convex-shaped, and the projected area of the arc-shaped structure accounts for 70%-100% of the upper surface area.

When the upper surface is arc-shaped, the radian is greater than 0 and less than π; preferably between π/20 and π/3; the arc is an inner arc or an outer arc;

When the shape of the upper surface is an overlapping arc, that is, an interlaced arc structure, the radian is greater than 0 and less than 2π; preferably between π/6 and π/2; the overlapping ratio of adjacent arc structures is 10 %~30%;

When the shape of the upper surface is concave-convex, that is, a concave-convex tangent arc structure, the radian is greater than 0 and less than 2π; preferably between π/6 and π/2;

The substrate and the P-type heavily doped material layer are all in the shape of a truncated cone with the same radius;

The N-type lightly doped material layer, the N-type transition material layer, the N-type lightly doped material layer, and the N-type heavily doped material layer have a trapezoidal cross-section as a whole; the internal angle range of the trapezoid is between 4° and 30° between;

The N-type lightly doped material layer accounts for 60% to 95% of the area of the P-type heavily doped material layer;

The width of the P-type ohmic electrode accounts for 10% to 90% of the exposed width of the P-type heavily doped material layer;

The width of the N-type ohmic electrode accounts for 2% to 20% of the radius of the N-type heavily doped material layer;

The material of the substrate is 4H-SiC, sapphire, Si or GaN;

The material of the P-type heavily doped material layer is SiC, GaO, Al _a1 In _b1 Ga _1-a1-b1 As or Al _x1 In _y1 Ga _1-x1-y1 N, and the composition of each element in the formula is 0≤a1 ≤1,0≤b1≤1,0≤1-a1-b1,0≤x1≤1,0≤y1≤1,0≤1-x1-y1, thickness 1～4μm, doping concentration 1×10 ¹⁷ cm ^-3 ～1×10 ²⁰ cm ^-3 ;

The material of the N-type lightly doped material layer is SiC, GaO, Al _a2 In _b2 Ga _1-a2-b2 As or Al _x2 In _y2 Ga _1-x2-y2 N, and the composition of each element in the formula is 0≤a2 ≤1,0≤b2≤1,0≤1-a2-b2,0≤x2≤1,0≤y2≤1,0≤1-x2-y2, thickness 0.1～2μm, doping concentration 5×10 ¹⁴ cm ^-3 ～1×10 ¹⁷ cm ^-3 ;

The material of the N-type transition material layer is SiC, GaO, Al _a3 In _b3 Ga _1-a3-b3 As or Al _x3 In _y3 Ga _1-x3-y3 N, and the composition of each element in the formula is 0≤a3≤1 ,0≤b3≤1,0≤1-a3-b3,0≤x3≤1,0≤y3≤1,0≤1-x3-y3, thickness is 0.1～2μm, doping concentration is 1×10 ¹⁷ cm ^-3 ～5×10 ¹⁸ cm ^-3 ;

The material of the N-type lightly doped material layer is SiC, GaO, Al _a4 In _b4 Ga _1-a4-b4 As or Al _x4 In _y4 Ga _1-x4-y4 N, and the composition of each element in the formula is 0≤a4 ≤1,0≤b4≤1,0≤1-a4-b4,0≤x4≤1,0≤y4≤1,0≤1-x4-y4, thickness 0.1～2μm, doping concentration 5×10 ¹⁴ cm ^-3 ～1×10 ¹⁷ cm ^-3 ;

The material of the N-type heavily doped material layer is SiC, GaO, Al _a5 In _b5 Ga _1-a5-b5 As or Al _x5 In _y5 Ga _1-x5-y5 N, and the composition of each element in the formula is 0≤a5 ≤1,0≤b5≤1,0≤1-a5-b5,0≤x5≤1,0≤y5≤1,0≤1-x5-y5, thickness 0.1～1μm, doping concentration 1×10 ¹⁷ cm ^-3 ～1×10 ²⁰ cm ^-3 ;

The material of the N-type ohmic electrode is Cr/Au or Ti/Au;

The material of the P-type ohmic electrode is Cr/Au or Ni/Au.

The preparation method of the photodetector structure with arc-shaped anti-reflection effect, the method comprises the following steps:

The first step is to use acetone, absolute ethanol, and deionized water to clean the substrate in sequence in the ultrasonic wave, with the growth side facing upward, and ultrasonic cleaning for 5 to 10 minutes each time;

In the second step, in the MOCVD or MBE reactor, a P-type heavily doped material layer with a thickness of 1-4 μm and an N-type lightly doped material layer with a thickness of 0.1-2 μm are epitaxially grown on the surface of the substrate after the first step. Miscellaneous material layer, N-type transition material layer with a thickness of 0.1-2 μm, N-type lightly doped material layer with a thickness of 0.1-2 μm, N-type heavily doped material layer with a thickness of 0.1-1 μm;

In the third step, on the N-type heavily doped material layer obtained in the second step, a tapered mesa is fabricated through photoresist variable temperature reflow technology and dry etching process, exposing the P-type heavily doped material layer, wherein the trapezoidal The inner angle range of the inclined mesa is between 4° and 30°, and the etched N-type lightly doped material layer accounts for 60% to 95% of the area of the P-type heavily doped material layer;

In the fourth step, an N-type ohmic electrode is prepared by evaporation above the mesa in the third step, and a P-type ohmic electrode is prepared by evaporation above the exposed P-type heavily doped material layer;

The fifth step is to prepare the remaining photosensitive area of the N-type ohmic electrode for the N-type heavily doped material layer in the fourth step, and make an arc-shaped patterned shape by photolithography and dry etching;

Thus, the above-mentioned photodetector structure with arc-shaped anti-reflection effect is obtained.

Substantive features of the present invention are:

The photosensitive area of the traditional epitaxial structure is a planar structure. When the light source is incident on the plane, part of the light will be reflected into the air and not enter the device. In the end, only a small part of the light will enter the device, resulting in poor photoresponsivity and severely restricting the detector. Sensitivity; while the photosensitive region of the epitaxial structure of the present invention is an arc structure, according to Fresnel's law, the critical angle of incident light decreases, which will reduce the reflectivity of light, resulting in a large increase of light incident into the device interior, and this The structure can make the distribution of light incident into the device more uniform, avoid a large accumulation of photogenerated carriers, and effectively improve the photoresponsivity and quantum efficiency.

The beneficial effects of the present invention are:

(1) The epitaxial structure of the photodetector of the present invention is that the photosensitive area between the N-type ohmic electrodes is etched into an arc structure. According to Fresnel's law, the critical angle of the incident light can be reduced as much as possible, and the light intensity can be reduced. Reflection probability, so that more light can enter the interior of the device, resulting in an increase in the transmittance of incident light by 10% to 50%, thereby increasing the photoresponsivity of the device by 10% to 50%, so that weak light source signals can be sensitively detected.

(2) The present invention utilizes the arc-shaped structure of the photosensitive region to make the distribution of light incident into the device more uniform, and the photogenerated carriers can be evenly distributed in the gain region of the device, which avoids the photogenerated carrier crowding and the generation of device self-sufficiency. Thermal effects, and more carriers generate gain at the same time, resulting in an increase in quantum efficiency of 10% to 50%.

(3) The method of the present invention has strong operability, low cost, simple and reliable process, and is suitable for popularization and use in industry.

The photodetector structure with arc-shaped anti-reflection effect of the invention is specially suitable for optoelectronic semiconductor devices, especially suitable for III-V wide bandgap semiconductor photodiodes.

Description of drawings

FIG. 1 is a schematic side sectional view of an epitaxial structure of a standard photodetector in the prior art, that is, it does not have an arc-shaped anti-reflection structure.

FIG. 2 is a schematic side cross-sectional view of an embodiment of a photodetector structure with an arc-shaped anti-reflection function according to the present invention.

Fig. 3 is the epitaxially grown P-type heavily doped material layer, N-type lightly doped material layer, N-type transition material layer, N-type lightly doped material layer and N-type heavily doped material layer for the standard photodetector in Example 1 Schematic diagram of the rear structure.

FIG. 4 is a schematic side sectional view of the product shown in FIG. 3 of Example 1, after the inclined mesa is etched by the photoresist variable temperature reflow technology.

FIG. 5 is a schematic top view of the structure of an arc-shaped anti-reflection photodetector used in Embodiment 1. FIG.

Fig. 6 is the light intensity distribution diagram of the traditional planar epitaxial structure and the photodetector structure with a kind of arc-shaped anti-reflection effect in embodiment 1; Wherein Fig. 6 a is the light intensity distribution diagram of the traditional planar epitaxial structure photodetector structure; Fig. 6b is a light intensity distribution diagram of a photodetector structure having an arc-shaped anti-reflection effect in embodiment 1;

FIG. 7 is a schematic side sectional view of the structure of an arc-shaped anti-reflection photodetector used in Embodiment 2. FIG.

FIG. 8 is a schematic top view of the structure of an arc-shaped anti-reflection photodetector used in Embodiment 2. FIG.

FIG. 9 is a schematic side sectional view of the structure of an arc-shaped anti-reflection photodetector used in Embodiment 3. FIG.

Among them, 101. Substrate, 102. P-type heavily doped material layer, 103. N-type lightly doped material layer, 104. N-type transition material layer, 105. N-type lightly doped material layer, 106. N-type heavily doped material layer Doped material layer, 107. P-type ohmic electrode, 108. N-type ohmic electrode.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but this should not be used as a limitation to the protection scope of the claims of the present application.

A photodetector structure (abbreviated as an epitaxial structure, see FIG. 2 ) with an arc-shaped anti-reflection effect of the present invention includes a substrate 101, a P-type heavily doped material layer 102, and an N-type lightly doped material in sequence along the epitaxial growth direction. Layer 103, N-type transition material layer 104, N-type lightly doped material layer 105, N-type heavily doped material layer 106, N-type ohmic electrode 108 and P-type ohmic electrode 107; the N-type heavily doped material layer 106 It is a photosensitive area with a thickness of 0.1-1μm. According to different device structure design requirements, the shape of the upper surface is arc-shaped (the arc is greater than 0 and less than 2π, preferably between π/6-3π/2), superimposed arc, Irregular patterns with curved surface structures such as concave and convex shapes.

The material of the substrate 101 in the epitaxial structure of the present invention may be but not limited to 4H-SiC, sapphire, Si or GaN;

The substrate and the P-type heavily doped material layer are all in the shape of a truncated cone with the same radius;

The N-type lightly doped material layer 103, the N-type transition material layer 104, the N-type lightly doped material layer 105, and the N-type heavily doped material layer 106 are in the shape of a conical cone (the section through the center is trapezoidal); trapezoidal The inner angle range is between 4° and 30°;

The P-type ohmic electrode 107 accounts for 10% to 90% of the exposed width of the P-type heavily doped material layer 102; The radius of the dopant material layer 102-the radius of the N-type lightly doped material layer 103) obtained ratio)

The width of the N-type ohmic electrode 108 (that is, the distance between the inner and outer edges) accounts for 2% to 20% of the radius of the N-type heavily doped material layer 106;

The material of the P-type heavily doped material layer 102 in the epitaxial structure of the present invention is SiC, GaO, Al _a1 In _b1 Ga _1-a1-b1 As or Al _x1 In _y1 Ga _1-x1-y1 N, where each element Composition 0≤a1≤1,0≤b1≤1,0≤1-a1-b1,0≤x1≤1,0≤y1≤1,0≤1-x1-y1, thickness 1～4μm, doped The concentration is 1×10 ¹⁷ cm ^-3 ～1×10 ²⁰ cm ^-3 ;

The material of the N-type lightly doped material layer 103 in the epitaxial structure of the present invention is SiC, GaO, Al _a2 In _b2 Ga _1-a2-b2 As or Al _x2 In _y2 Ga _1-x2-y2 N, where each element Composition 0≤a2≤1,0≤b2≤1,0≤1-a2-b2,0≤x2≤1,0≤y2≤1,0≤1-x2-y2, thickness 0.1～2μm, doped The concentration is 5×10 ¹⁴ cm ^-3 ～1×10 ¹⁷ cm ^-3 ;

The material of the N-type transition material layer 104 in the epitaxial structure of the present invention is SiC, GaO, Al _a3 In _b3 Ga _1-a3-b3 As or Al _x3 In _y3 Ga _1-x3-y3 N, the composition of each element in the formula 0≤a3≤1,0≤b3≤1,0≤1-a3-b3,0≤x3≤1,0≤y3≤1,0≤1-x3-y3, thickness is 0.1～2μm, doping concentration is 1×10 ¹⁷ cm ^-3 ～5×10 ¹⁸ cm ^-3 ;

The material of the N-type lightly doped material layer 105 in the epitaxial structure of the present invention is SiC, GaO, Al _a4 In _b4 Ga _1-a4-b4 As or Al _x4 In _y4 Ga _1-x4-y4 N, the elements in the formula Composition 0≤a4≤1,0≤b4≤1,0≤1-a4-b4,0≤x4≤1,0≤y4≤1,0≤1-x4-y4, thickness 0.1～2μm, doped The concentration is 5×10 ¹⁴ cm ^-3 ～1×10 ¹⁷ cm ^-3 ;

The material of the N-type heavily doped material layer 106 in the epitaxial structure of the present invention is SiC, GaO, Al _a5 In _b5 Ga _1-a5-b5 As or Al _x5 In _y5 Ga _1-x5-y5 N, and the elements in the formula Composition 0≤a5≤1,0≤b5≤1,0≤1-a5-b5,0≤x5≤1,0≤y5≤1,0≤1-x5-y5, thickness 0.1～1μm, doped The concentration is 1×10 ¹⁷ cm ^-3 ～1×10 ²⁰ cm ^-3 ;

The material of the N-type ohmic electrode 108 is Cr/Au or Ti/Au;

The material of the P-type ohmic electrode 107 is Cr/Au or Ni/Au.

A kind of preparation method of the photodetector structure with arc anti-reflection effect of the present invention, the steps of this method are as follows:

In the first step, the substrate is cleaned with acetone, absolute ethanol, and deionized water sequentially in ultrasound, with the growth side facing up, and ultrasonic cleaning is performed for 5 to 10 minutes each time to remove foreign matter attached to the surface of the substrate 101;

In the second step, in the MOCVD or MBE reactor, on the surface of the substrate treated in the first step, epitaxial growth with a thickness of 1-4 μm and a doping concentration of 1×10 ¹⁷ cm ^-3 to 1×10 ²⁰ cm ^{- 3} P-type heavily doped material layer 102 with a thickness of 0.1-2 μm, and an N ^- type lightly doped material layer 103 with a thickness of 0.1-2 μm with a doping concentration of 5×10 ¹⁴ cm ⁻³ to 1×10 ¹⁷ cm N ^- type transition material layer 104 with a thickness of 0.1 to 2 μm and a doping concentration of ^{5×10 14 cm -3 to 1} ×10 An N-type lightly doped material layer 105 with a thickness of ¹⁷ cm- ³ , an N-type heavily doped material layer 106 with a thickness of 0.1-1 μm and a doping concentration of 1×10 ¹⁷ cm ^-3 to 1×10 ²⁰ cm ^-3 ;

In the third step, on the N-type heavily doped material layer 106 obtained in the second step, an inclined mesa is fabricated by photoresist variable temperature reflow technology and dry etching process, exposing the P-type heavily doped material layer 102, wherein, The inner angle range of the trapezoidal inclined mesa is between 4° and 30°, and the etched N-type lightly doped material layer 103 accounts for 60% to 95% of the area of the P-type heavily doped material layer 102;

The fourth step is to prepare an N-type ohmic electrode 108 by evaporation on the N-type heavily doped material layer 106 obtained in the third step, and prepare a P-type ohmic electrode 107 by evaporation on the exposed P-type heavily doped material layer 102;

The fifth step is to prepare the remaining photosensitive area of the N-type ohmic electrode 108 for the N-type heavily doped material layer 106 in the fourth step, and make an arc-shaped patterned shape by photolithography and dry etching, according to different device structure design requirements , the shape of the upper surface is arc-shaped (the radian is greater than 0 and less than 2π, preferably between π/6 and 3π/2), overlapping arcs, concave-convex shapes and other irregular patterns with arc-shaped structures;

Thus, the above-mentioned photodetector structure with arc-shaped anti-reflection effect is obtained.

After our research, we found that since most of the detection light sources are not parallel light sources, there will be serious reflections in the planar structure. If the photosensitive area of the detection device is made into an arc structure, according to Fresnel's law, the light transmittance will be greatly increased, thereby The complex process steps of preparing the anti-reflection film are omitted.

The invention utilizes the arc-shaped anti-reflection structure to reduce the critical angle of incident light, reduce the reflectivity, and increase the transmittance of the light source, thereby enhancing the light responsivity of the device and improving the detector's ability to detect weak signal light sources.

FIG. 1 is a schematic side sectional view of the epitaxial structure of a standard photodetector in the prior art, which sequentially includes a substrate 101, a P-type heavily doped material layer 102, an N-type lightly doped material layer 103, and an N-type lightly doped material layer along the epitaxial growth direction. N-type transition material layer 104, N-type lightly doped material layer 105, N-type heavily doped material layer 106, N-type ohmic electrode 108 and P-type ohmic electrode 107.

Fig. 2 is a schematic side sectional view of an embodiment of a photodetector structure with an arc-shaped anti-reflection effect according to the present invention, which includes in sequence along the epitaxial growth direction: a substrate 101, a P-type heavily doped material layer 102, an N-type light Doping material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 , N-type heavily doped material layer 106 , N-type ohmic electrode 108 and P-type ohmic electrode 107 .

Fig. 3 shows that the standard photodetector of Embodiment 1 has epitaxially grown a P-type heavily doped material layer 102, an N-type lightly doped material layer 103, an N-type transition material layer 104, and an N-type lightly doped material layer along the substrate 101. 105 and the N-type heavily doped material layer 106 is a schematic side cross-sectional view of the structure.

Fig. 4 is the product shown in Fig. 3 of Example 1, a schematic side sectional view of the structure after the inclined mesa is etched by the photoresist variable temperature reflow technology, and it includes in sequence along the epitaxial growth direction: a substrate 101, a P-type heavily doped Material layer 102 , N-type lightly doped material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 and N-type heavily doped material layer 106 .

5 is a top view schematic diagram of a photodetector structure with an arc-shaped anti-reflection effect adopted in Embodiment 1, which includes: a P-type ohmic electrode 107, a P-type heavily doped material layer 102, and an N-type lightly doped material layer from outside to inside. Material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 , N-type heavily doped material layer 106 and N-type ohmic electrode 108 .

Fig. 6 is the light intensity distribution diagram of the traditional planar epitaxial structure and the photodetector structure with arc-shaped anti-reflection effect in Embodiment 1. It can be clearly seen from the figure that for the traditional planar epitaxial structure, the light incident on the device Afterwards, the interior mainly gathers in the middle of the device, and after adopting the arc-shaped anti-reflection structure, the distribution of incident light inside the device is relatively more uniform, which can effectively avoid the accumulation of a large number of photogenerated carriers and reduce the self-heating effect of the device caused by the accumulation of carriers. More carriers undergo impact ionization, which improves the photoresponsivity and quantum efficiency of the detector.

Fig. 7 is a schematic side sectional view of a curved anti-reflection photodetector structure adopted in Embodiment 2, which sequentially includes a substrate 101, a P-type heavily doped material layer 102, an N-type lightly doped material layer along the epitaxial growth direction. Impurity material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 , N-type heavily doped material layer 106 , N-type ohmic electrode 108 and P-type ohmic electrode 107 .

Fig. 8 is a top view schematic diagram of an arc-shaped anti-reflection photodetector structure adopted in Embodiment 2, which includes: P-type ohmic electrode 107, P-type heavily doped material layer 102, N-type lightly doped material layer from outside to inside Material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 , N-type heavily doped material layer 106 and N-type ohmic electrode 108 .

Fig. 9 is a schematic side sectional view of an arc-shaped anti-reflection photodetector structure adopted in Embodiment 3, which sequentially includes a substrate 101, a P-type heavily doped material layer 102, an N-type lightly doped material layer along the epitaxial growth direction. Impurity material layer 103 , N-type transition material layer 104 , N-type lightly doped material layer 105 , N-type heavily doped material layer 106 , N-type ohmic electrode 108 and P-type ohmic electrode 107 .

Example 1

In this embodiment, a photodetector structure with an arc-shaped anti-reflection effect, the epitaxial structure sequentially includes a substrate 101, a P-type heavily doped material layer 102, and an N-type lightly doped material layer 103 along the epitaxial growth direction. , N-type transition material layer 104, N-type lightly doped material layer 105, N-type heavily doped material layer 106, N-type ohmic electrode 108 and P-type ohmic electrode 107, wherein the thickness of N-type heavily doped material layer 106 is 0.3 μm, doping concentration of 1×10 ¹⁹ cm ^-3 , the shape of the photosensitive region is a single concave arc surface of π/3 radians, and the projected area of the arc structure accounts for 100% of the upper surface area. Wherein, the diameter of the substrate 101 is 800 μm, the diameter of the N-type lightly doped material layer 103 is 700 μm, the width of the P-type ohmic electrode 107 is 50 μm, and the width of the N-type ohmic electrode 108 is 50 μm.

In the above, the substrate 101 is 4H-SiC; the material of the P-type heavily doped material layer 102 is SiC, the thickness is 3 μm, and the doping concentration is 1×10 ¹⁹ cm ^-3 ; the material of the N-type lightly doped material layer 103 is SiC with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁵ cm ^-3 ; the N-type transition material layer 104 is made of SiC with a thickness of 0.1 μm and a doping concentration of 1×10 ¹⁸ cm ^-3 ; N-type lightly doped The impurity material layer 105 is made of SiC with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁵ cm ⁻³ ; the N-type heavily doped material layer 106 is made of SiC with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁹ cm ⁻³ ; the material of the N-type ohmic electrode 108 is Ti/Au; the material of the P-type ohmic electrode 107 is Ni/Au.

The above-mentioned photodetector structure with arc-shaped anti-reflection effect has a preparation method as follows:

In the first step, the substrate is cleaned by using acetone, absolute ethanol, and deionized water in sequence in the ultrasonic wave, with the growth side facing up, and ultrasonic cleaning is performed for 8 minutes each time to remove foreign matter attached to the surface of the substrate 101;

In the second step, in the MOCVD reaction furnace, a silicon carbide P-type heavily doped material layer 102 with a thickness of 3 μm and a doping concentration of 1×10 ¹⁹ cm ^-3 is sequentially epitaxially grown on the surface of the substrate treated in the first step , a silicon carbide N-type lightly doped material layer 103 with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁵ cm ^-3 , an N-type transition material with a thickness of 0.2 μm and a doping concentration of 1×10 ¹⁸ cm ^-3 Layer 104, an N-type lightly doped material layer 105 with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁵ cm ^-3 , and an N-type heavily doped material with a thickness of 0.3 μm and a doping concentration of 1×10 ¹⁹ cm ^-3 For the heterogeneous material layer 106, the growth temperature is 1500° C., and the air pressure is 80 mbar;

In the third step, on the N-type heavily doped material layer 106 obtained in the second step, an inclined mesa is fabricated by photoresist variable temperature reflow technology and dry etching process, exposing the P-type heavily doped material layer 102, wherein, The inner angle of the trapezoidal inclined mesa is 8°, and the etched N-type lightly doped material layer 103 accounts for 89% of the area of the P-type heavily doped material layer 102;

In the fourth step, an N-type ohmic electrode 108 is prepared by vapor deposition on the N-type heavily doped material layer 106 obtained in the third step, and a P-type ohmic electrode 107 is prepared by vapor deposition on the exposed P-type heavily doped material layer 102, wherein , the P-type ohmic electrode 107 accounts for 50% of the exposed width of the P-type heavily doped material layer 102, and the P-type ohmic electrode 107 and the N-type ohmic electrode 108 are both ring-shaped;

The fifth step is to prepare the remaining photosensitive area of the N-type ohmic electrode 108 for the N-type heavily doped material layer 106 in the fourth step. By coating photoresist, exposing and developing, the place that does not need to be etched is used for photolithography Glue protection, remove the photoresist where etching is required, and then use ICP dry etching to make arc-shaped patterned shapes by adjusting the moving rate of the stage and the etching power of the ICP equipment. According to the design requirements of the device structure, The shape of the upper surface of the photosensitive area is a concave arc surface of π/3 radian;

Thus, a photodetector structure with arc-shaped anti-reflection effect of this embodiment is obtained.

Figure 6 is a schematic diagram of the light intensity distribution. It can be clearly seen from the figure that for the traditional planar epitaxy structure, the light is mainly concentrated in the middle of the device after it is incident inside the device, but after the arc-shaped anti-reflection structure is adopted, the incident light The distribution inside the device is relatively more uniform, effectively avoiding a large amount of accumulation of photogenerated carriers, and improving the photoresponsivity and quantum efficiency of the detector.

Example 2

In this embodiment, a photodetector structure with an arc-shaped anti-reflection effect, the epitaxial structure sequentially includes a substrate 101, a P-type heavily doped material layer 102, and an N-type lightly doped material layer 103 along the epitaxial growth direction. , N-type transition material layer 104, N-type lightly doped material layer 105, N-type heavily doped material layer 106, N-type ohmic electrode 108 and P-type ohmic electrode 107, wherein the thickness of N-type heavily doped material layer 106 is 0.3μm, the doping concentration is 1×10 ¹⁹ cm ^-3 , the shape of the photosensitive area is a π/4 radian concave and convex arc surface, and the diameter of each arc surface (that is, the diameter of the arc itself) is 100 μm. The projected area of the structure accounts for 95% of the upper surface area, and the adjacent concave and convex arcs are just tangent.

In the above, the substrate 101 is sapphire; the material of the P-type heavily doped material layer 102 is Al _0.4 Ga _0.6 N, the thickness is 2.5 μm, and the doping concentration is 2×10 ¹⁸ cm ^-3 ; the N-type lightly doped material layer 103 is made of Al _0.4 Ga _0.6 N with a thickness of 0.2 μm and a doping concentration of 1×10 ¹⁶ cm ^-3 ; the N-type transition material layer 104 is made of Al _0.4 Ga _0.6 N with a thickness of 0.1 μm and a doping concentration of 1 ×10 ¹⁸ cm ^-3 ; N-type lightly doped material layer 105 is made of Al _0.4 Ga _0.6 N with a thickness of 0.2 μm and a doping concentration of 1×10 ¹⁶ cm ^-3 ; N-type heavily doped material layer 106 is made of Al _0.45 Ga _0.55 N, thickness 0.3 μm, doping concentration 2×10 ¹⁸ cm ⁻³ ; N-type ohmic electrode 108 is made of Cr/Au; P-type ohmic electrode 107 is made of Cr/Au.

The above-mentioned photodetector structure with arc-shaped anti-reflection effect has a preparation method as follows:

In the first step, the substrate is cleaned by using acetone, absolute ethanol, and deionized water in sequence in the ultrasonic wave, with the growth side facing up, and ultrasonic cleaning is performed for 8 minutes each time to remove foreign matter attached to the surface of the substrate 101;

In the second step, in the MOCVD reaction furnace, an Al _0.4 Ga _0.6 N material layer 102 with a thickness of 2.5 μm and a doping concentration of 2×10 ¹⁸ cm ⁻³ is epitaxially grown sequentially on the surface of the substrate treated in the first step, Al _0.4 Ga _0.6 N material layer 103 with a thickness of 0.2 μm and a doping concentration of 1×10 ¹⁶ cm ^-3 , and an Al _0.4 Ga _0.6 N material layer with a thickness of 0.1 μm and a doping concentration of 1×10 ¹⁸ cm ^-3 104, an Al _0.4 Ga _0.6 N material layer with a thickness of 0.2 μm and a doping concentration of 1×10 ¹⁶ cm ⁻³ 105, an Al _0.45 Ga _0.55 N material layer with a thickness of 0.3 μm and a doping concentration of 2×10 ¹⁸ cm ⁻³ For the material layer 106, the growth temperature is 970° C., and the air pressure is 90 mbar;

In the third step, on the N-type heavily doped material layer 106 obtained in the second step, an inclined mesa is fabricated by photoresist variable temperature reflow technology and dry etching process, exposing the P-type heavily doped material layer 102, wherein, The inner angle of the trapezoidal inclined mesa is 8°, and the etched N-type lightly doped material layer 103 accounts for 89% of the area of the P-type heavily doped material layer 102;

In the fourth step, an N-type ohmic electrode 108 is prepared by vapor deposition on the N-type heavily doped material layer 106 obtained in the third step, and a P-type ohmic electrode 107 is prepared by vapor deposition on the exposed P-type heavily doped material layer 102, wherein , the P-type ohmic electrode 107 accounts for 50% of the exposed width of the P-type heavily doped material layer 102;

The fifth step is to prepare the remaining photosensitive area of the N-type ohmic electrode 108 for the N-type heavily doped material layer 106 in the fourth step. By coating photoresist, exposing and developing, the place that does not need to be etched is used for photolithography Protected by glue, remove the photoresist where it needs to be etched, and then use ICP dry etching to make a convex patterned shape by adjusting the moving rate of the stage and the etching power of the ICP equipment; then coat the sample Photoresist, exposure and development, protect the convex patterned structure with photoresist, remove the photoresist where it needs to be etched, and also use ICP dry etching, by adjusting the moving rate of the stage and ICP equipment The etching power is used to make a concave patterned shape, and the pattern shape required by the device structure design is obtained. The shape of the photosensitive area is a curved surface with alternating concave and convex in π/4 radians;

Thus, a photodetector structure with arc-shaped anti-reflection effect of this embodiment is obtained.

Example 3

The composition and connection of the various parts of this embodiment are the same as those of Embodiment 1, except that the shape of the photosensitive region of the topmost N-type heavily doped material layer 106 in this embodiment is an arc superimposed by concave curved surfaces of π/6 radians. Surface structure, in which the diameter of each arc surface is 150 μm, the overlap between adjacent arc surfaces is 10%, the projected area of the arc structure accounts for 98% of the upper surface area, and the transmittance of incident light is increased by 20% compared with the current planar structure %, thereby increasing the photoresponsivity of the device by 10%.

All the above-mentioned embodiments can reduce the light reflectance of the surface, increase the light transmittance, and improve the light responsivity and sensitivity of the detector, and the method of the present invention has strong operability, simple process, low cost and easy implementation.

The raw materials involved in the present invention can be obtained through known channels, and the operating techniques in the preparation methods are within the grasp of those skilled in the art.

What is not mentioned in the present invention is applicable to the prior art.

Claims (5)

1. a kind of photodetector structure with the anti-reflection effect of arc, it is characterized in that the structure along epitaxial growth direction successively Material layer, N-type transition material layer, N-type is lightly doped including substrate, p-type heavily doped material layer, N-type, material layer, N-type weight is lightly doped Dopant material layer and N-type Ohmic electrode；P-type Ohmic electrode is located at the p-type heavily doped material layer that N-type is lightly doped on the outside of material layer On；Wherein, N-type Ohmic electrode is annular shape, positioned at the outer rim of N-type heavily doped material layer, the N-type heavy doping material that appears among it The bed of material is photosensitive area, and with a thickness of 0.1~1 μm, arcuate structure is contained in the upper surface of the photosensitive area, the arcuate structure Projected area accounts for the 70%~100% of upper surface area.

2. as described in claim 1 with the photodetector structure of the anti-reflection effect of arc, it is characterized in that the arc knot Structure is arc, folded arc or concave-convex；

When upper surface is arc, the radian is greater than 0, and is less than π；Preferably between pi/2 0~π/3；The arc is Inner arc or outer arc；

When the shape of upper surface is folded arc, i.e., interlaced arcuate structure, the radian is greater than 0, and less than 2 π；It is preferred that Between π/6~pi/2；Adjacent arcuate structure overlap proportion is 10%~30%；

When the shape of upper surface is concave-convex, i.e., concave-convex tangent arcuate structure, the radian is greater than 0, and less than 2 π；It is excellent It is selected as between π/6~pi/2.

3. as described in claim 1 with the photodetector structure of the anti-reflection effect of arc, it is characterized in that the substrate, P Type heavily doped material layer be it is round table-like, radius is identical；

The N-type is lightly doped that material layer is lightly doped in material layer, N-type transition material layer, N-type, N-type heavily doped material layer is integrally in Section is trapezoidal rotary table；Trapezoidal interior angular region is between 4 °~30 °；

60%~95% that material layer accounts for p-type heavily doped material level product is lightly doped in the N-type；

The width of the p-type Ohmic electrode accounts for p-type heavily doped material layer and exposes the 10%~90% of width；

The width of the N-type Ohmic electrode accounts for the 2%~20% of N-type heavily doped material layer radius.

4. as described in claim 1 with the photodetector structure of the anti-reflection effect of arc, it is characterized in that the material of the substrate Matter is 4H-SiC, sapphire, Si or GaN；

The material of the p-type heavily doped material layer is SiC, GaO, Al_a1In_b1Ga_1-a1-b1As or Al_x1In_y1Ga_1-x1-y1N, it is each in formula Component 0≤a1≤1,0≤b1≤1,0≤1-a1-b1,0≤x1≤1,0≤y1≤1, the 0≤1-x1-y1 of element, with a thickness of 1~ 4 μm, doping concentration is 1 × 10¹⁷cm^-3~1 × 10²⁰cm^-3；

The material that material layer is lightly doped in the N-type is SiC, GaO, Al_a2In_b2Ga_1-a2-b2As or Al_x2In_y2Ga_1-x2-y2N, it is each in formula Component 0≤a2≤1,0≤b2≤1,0≤1-a2-b2,0≤x2≤1,0≤y2≤1, the 0≤1-x2-y2 of element, with a thickness of 0.1 ~2 μm, doping concentration is 5 × 10¹⁴cm^-3~1 × 10¹⁷cm^-3；

The material of the N-type transition material layer is SiC, GaO, Al_a3In_b3Ga_1-a3-b3As or Al_x3In_y3Ga_1-x3-y3N, each member in formula Component 0≤a3≤1,0≤b3≤1,0≤1-a3-b3,0≤x3≤1,0≤y3≤1, the 0≤1-x3-y3 of element, with a thickness of 0.1~ 2 μm, doping concentration is 1 × 10¹⁷cm^-3~5 × 10¹⁸cm^-3；

The material that material layer is lightly doped in the N-type is SiC, GaO, Al_a4In_b4Ga_1-a4-b4As or Al_x4In_y4Ga_1-x4-y4N, it is each in formula Component 0≤a4≤1,0≤b4≤1,0≤1-a4-b4,0≤x4≤1,0≤y4≤1, the 0≤1-x4-y4 of element, with a thickness of 0.1 ~2 μm, doping concentration is 5 × 10¹⁴cm^-3~1 × 10¹⁷cm^-3；

The material of the N-type heavily doped material layer is SiC, GaO, Al_a5In_b5Ga_1-a5-b5As or Al_x5In_y5Ga_1-x5-y5N, it is each in formula Component 0≤a5≤1,0≤b5≤1,0≤1-a5-b5,0≤x5≤1,0≤y5≤1, the 0≤1-x5-y5 of element, with a thickness of 0.1 ~1 μm, doping concentration is 1 × 10¹⁷cm^-3~1 × 10²⁰cm^-3；

The material of the N-type Ohmic electrode is Cr/Au or Ti/Au；

The material of the p-type Ohmic electrode is Cr/Au or Ni/Au.

5. the preparation method of the photodetector structure with the anti-reflection effect of arc, this method include as described in claim 1 Following steps:

The first step successively cleans substrate using acetone, dehydrated alcohol, deionized water in ultrasound, and growth is face-up, often Secondary ultrasonic cleaning 5~10 minutes；

Second step, in MOCVD MBE reacting furnace, the successively epitaxial growth thickness on the first step treated substrate surface Material layer is lightly doped for 1~4 μm of p-type heavily doped material layer, with a thickness of 0.1~2 μm of N-type, with a thickness of 0.1~2 μm of N-type Material layer is lightly doped, with a thickness of 0.1~2 μm of N-type with a thickness of 0.1~1 μm of N-type heavily doped material layer in transition material layer；

Third step passes through photoresist alternating temperature technique of backflow and dry etching work on the N-type heavily doped material layer that second step obtains Skill make taper table top, expose p-type heavily doped material layer, wherein in trapezoidal inclined table angular region be located at 4 °~30 ° it Between, 60%~95% that material layer accounts for p-type heavily doped material level product is lightly doped in the N-type after etching；

4th step obtains vapor deposition preparation N-type Ohmic electrode above table top in third step, on exposing p-type heavily doped material layer Side's vapor deposition preparation p-type Ohmic electrode；

5th step has prepared the remaining photosensitive area of N-type Ohmic electrode for the 4th step N-type heavily doped material layer, by photoetching and Dry etching makes arc patterns shape；

Thus a kind of photodetector structure with the anti-reflection effect of arc is obtained.