A high-responsivity detector in the 850nm band

Abstract

The present invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a 850nm band high-responsivity detector, the difference of which is that it includes an n-type substrate located at the bottom of the detector, and the n-type substrate includes an aluminum oxide layer, an n-type contact layer, an n-type DBR layer, a lower limiting layer, an absorption layer, an upper limiting layer, a p-type contact layer and an anti-reflection film layer from bottom to top, and also includes an n-type electrode layer and a p-type electrode layer, the n-type electrode layer is located on the n-type contact layer and on one side of the n-type DBR layer, and the p-type electrode layer is located on the p-type contact layer and on one side of the anti-reflection film layer. The present invention improves the response rate and is conducive to the realization of a radiation-resistant low dark current high-responsivity detector.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a high-responsivity detector in the 850nm band. Background Art

[0002] Semiconductor photodetectors are the most ideal photodetectors due to their small size, high sensitivity, fast response speed and easy integration. Typical examples include PIN photodiodes, avalanche diodes and silicon photomultiplier tubes. They are widely used in fiber optic communications, sensor systems, high energy physics, nuclear medicine and other fields.

[0003] PIN photodiode is a detector with a lightly doped intrinsic region between pn diodes. The internal electric field across the two ends changes with the distance from the diode surface. The electric field in the intrinsic region of PIN photodiode is very strong. When a photon is absorbed in this region, the photon energy is converted to new carriers (electron and hole pairs). These newly generated carriers drift in different directions (electrons toward the n region and holes toward the p region) under the action of the electric field according to their own polarity. If the external circuit is connected again, a photocurrent is generated at this time. Since PIN photodiode has a wide intrinsic region, it has a longer light wave absorption region and a faster time response. It has many applications, such as attenuators, RF switches, and detectors in fiber optic systems. Its noise is mainly dark current and shot noise generated by discrete photons of light. PIN photodiode has good photoelectric properties, simple structure, easy production and processing, and has a small dark current. PIN photodiode works stably for a long time and only needs to load a low bias voltage.

[0004] Conventional 850nm band photodetectors generally use silicon detectors, but the response rate of silicon detectors is not high. Conventional light source materials are all III-V material systems, and the two are difficult to integrate into a monolithic chip, which limits the high-integration development of large-scale optoelectronic integration. Silicon materials are not as resistant to radiation as GaAs materials. The development of 5G has promoted the development of GaAs-based high-speed and high-power electronic devices, and expanded the application areas of GaAs materials in future optoelectronic integration. For applications such as space optical communications and laser batteries, GaAs-based detectors are very suitable, but the defect density of GaAs semi-insulating substrates is very high, reaching 10,000 / cm 2 , which is at least one order of magnitude higher than that of N-type substrates. Therefore, using GaAs semi-insulating substrates will lead to more detector defects and is not suitable for detector arrays. There are a series of problems such as excessive dark current, uneven response, and low yield. Directly using N-type substrates, although the defects are low, its conductivity has serious parasitic effects, which affects the detection speed.

[0005] In view of this, in order to overcome the above technical defects, providing a high-responsivity detector in the 850nm band has become an urgent problem to be solved in this field. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-responsivity detector in the 850nm band to improve the response rate and contribute to the realization of a radiation-resistant, low-dark-current, high-responsivity detector.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a 850nm band high-responsivity detector, the difference of which is that: it includes an n-type substrate located at the bottom of the detector, and the n-type substrate includes, from bottom to top, an aluminum oxide layer, an n-type contact layer, an n-type DBR layer, a lower limiting layer, an absorption layer, an upper limiting layer, a p-type contact layer and an anti-reflection film layer, and also includes an n-type electrode layer and a p-type electrode layer, the n-type electrode layer is located on the n-type contact layer and on one side of the n-type DBR layer, and the p-type electrode layer is located on the p-type contact layer and on one side of the anti-reflection film layer.

[0008] According to the above technical solution, the n-type substrate is a GaAs material with ultra-low defect density and a thickness of 80-150 μm.

[0009] According to the above technical solution, the Al content in the aluminum oxide layer is greater than 98% and the thickness is 10-40nm.

[0010] According to the above technical solution, the n-type doping concentration of the n-type contact layer is greater than 1x 10 18 / cm 3 , thickness is 30-100nm.

[0011] According to the above technical solution, the n-type DBR layer is a plurality of high / low aluminum component AlGaAs film pairs, each of which is composed of 850 / 4nm optical thickness high aluminum AlGaAs and 850 / 4nm optical thickness low aluminum AlGaAs, and the n-type doping concentration is 5x 10 17 / cm 3 Up to 1x 10 18 / cm 3 .

[0012] According to the above technical solution, the high aluminum AlGaAs is Al 0.7 GaAs, low aluminum AlGaAs is Al 0.1 GaAs, the total number of the thin film pairs is 10-20 pairs.

[0013] According to the above technical solution, the lower limiting layer is i-type AlGaAs material, the Al component is 0.2-0.5, and the thickness is 100-300nm; the absorption layer is i-type GaAs material, the thickness is greater than 1μm; the upper limiting layer is i-type AlGaAs material, the Al component is 0.2-0.5, and the thickness is 100-300nm.

[0014] According to the above technical solution, the p-type contact layer is a p-type graded doping material with a total thickness of 110nm; the lower part is an AlGaAs graded layer, and the Al component is gradually reduced from the bottom to the upper GaAs contact surface of the AlGaAs material. The highest Al component content is 0.3, which gradually decreases to 0.2, with a thickness of 100nm, and the p-type doping concentration is 2x 10 17 / cm 3 Up to 1x 10 18 / cm 3 ; The thickness of the GaAs contact surface is 10nm, and the P-type doping concentration is 1x 10 19 / cm 3 .

[0015] According to the above technical solution, the antireflection film layer is a double-layer mixed structure, including a lower titanium oxide layer and an upper silicon oxide layer, and the sum of their optical thicknesses is one quarter of 850nm.

[0016] According to the above technical solution, the n-type electrode layer is AuGeNi / Au material with a total thickness of 300-500nm; the p-type electrode layer is a TiAu bimetallic layer with a total thickness of 400-500nm.

[0017] According to the above scheme, the present invention discloses a 850nm band high-responsivity detector. The present invention reduces the parasitic capacitance of the 850nm band GaAs-based photodetector substrate through a new design. By introducing an aluminum oxide layer on an N-type substrate and using a wet oxygen process to manufacture an insulating layer, the effect of reducing parasitic capacitance and improving the response rate can be achieved by coordinating the structures of other layers. It is suitable for medium and short-distance high-speed optical communications, and is helpful for the realization of radiation-resistant low dark current high-responsivity detectors. The present invention can be applied to the fields of optical communications, radiation-resistant detection, space energy transmission, photon integration and laser batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the overall structure of the laser according to the embodiment of the present invention;

[0019] Figure 2 This is a structural diagram of an epitaxial material according to an embodiment of the present invention;

[0020] Among them: 10 - n-type substrate, 20 - aluminum oxide layer, 30 - n-type contact layer, 40 - n-type electrode layer, 50 - n-type DBR layer, 60 - lower limiting layer, 70 - absorption layer, 80 - upper limiting layer, 90 - p-type contact layer, 100 - p-type electrode layer, 110 - anti-reflection film layer. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] Hereinafter, many aspects of the present invention will be better understood with reference to the accompanying drawings. The components in the accompanying drawings are not necessarily drawn to scale. Instead, emphasis is placed on clearly illustrating the components of the present invention. In addition, in several views of the accompanying drawings, the same reference numerals indicate corresponding parts.

[0023] As used herein, the words "exemplary" or "illustrative" mean used as an example, instance, or illustration. Any implementation described herein as "exemplary" or "illustrative" is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations, which are provided to enable those skilled in the art to make and use embodiments of the present disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. In other implementations, well-known features and methods are described in detail so as not to obscure the present invention. For the purposes of the description herein, the terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," and their derivatives will be used interchangeably. Figure 1 The invention is directed to the invention of the present invention. Moreover, there is no intention to be bound by any express or implied theory given in the preceding technical field, background technology, summary of the invention or the detailed description below. It should also be understood that the specific devices and processes shown in the drawings and described in the following description are simple exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be understood as limiting unless the claims explicitly state otherwise.

[0024] Please refer to Figure 1 and Figure 2The invention discloses a 850nm band high-responsivity detector, which is different in that it includes an n-type substrate 10 located at the bottom of the detector, and the n-type substrate 10 includes an aluminum oxide layer 20, an n-type contact layer 30, an n-type DBR layer 50, a lower limiting layer 60, an absorption layer 70, an upper limiting layer 80, a p-type contact layer 90 and an anti-reflection film layer 110 from bottom to top, and also includes an n-type electrode layer 40 and a p-type electrode layer 100. The n-type electrode layer 40 is located on the n-type contact layer 30 and on one side of the n-type DBR layer 50, and the p-type electrode layer 100 is located on the p-type contact layer 90 and on one side of the anti-reflection film layer 110. The n-type contact layer 30 has an n-type electrode layer 40 at the left end and an n-type DBR layer 50 at the right end. The p-type contact layer 90 has a p-type electrode layer 100 at the left end and an anti-reflection film layer 110 at the right end.

[0025] Specifically, the n-type substrate 10 is a GaAs material with ultra-low defect density, and has a thickness of 80-150 μm. The defect density of n-type GaAs material can be reduced by more than one order of magnitude compared with p-type and semi-insulating GaAs.

[0026] Specifically, the aluminum oxide layer 20 has an Al content greater than 98% and a thickness of 10-40 nm. This layer of material is not grown directly on the n-type substrate 10, but is formed by growing AlAs or AlGaAs high-aluminum-containing materials on the n-type substrate 10 during the device process stage, and by a side wet oxygen process, wherein the Al content of the group III elements is greater than 98%.

[0027] Specifically, the n-type doping concentration of the n-type contact layer 30 is greater than 1× 10 18 / cm 3 The thickness is 30-100 nm. It is grown on the AlAs or AlGaAs high aluminum-containing material on the above n-type substrate 10 by using MOCVD or MBE equipment in the epitaxial stage.

[0028] Preferably, the n-type DBR layer 50 is a plurality of high / low aluminum component AlGaAs film pairs, each of which is composed of 850 / 4nm optical thickness high aluminum AlGaAs and 850 / 4nm optical thickness low aluminum AlGaAs, and the n-type doping concentration is 5x10 17 / cm 3 Up to 1x 10 18 / cm 3 The n-type DBR layer 50 is located on the right side of the n-type contact layer 30 .

[0029] Preferably, the high aluminum AlGaAs is Al 0.7 GaAs, low aluminum AlGaAs is Al 0.1 GaAs, the total number of the thin film pairs is 10-20 pairs.

[0030] Specifically, the lower limiting layer 60 is i-type AlGaAs material, which is an unintentional doped material, with an Al component of 0.2-0.5 and a thickness of 100-300nm; the absorption layer 70 is i-type GaAs material, which is an unintentional doped material, with a thickness greater than 1μm; the upper limiting layer 80 is i-type AlGaAs material, which is an unintentional doped material, with an Al component of 0.2-0.5 and a thickness of 100-300nm.

[0031] Specifically, the p-type contact layer 90 is a p-type graded doping material with a total thickness of 110 nm; the lower part is an AlGaAs graded layer, in which the Al component of the AlGaAs material gradually decreases from bottom to top until the GaAs contact surface at the top, the highest Al component content is 0.3, which gradually decreases to 0.2, and the thickness is 100 nm. The p-type doping concentration is 2x 10 17 / cm 3 Up to 1x 10 18 / cm 3 ; The thickness of the GaAs contact surface is 10nm, and the P-type doping concentration is 1x 10 19 / cm 3 .

[0032] Preferably, the antireflection film layer 110 is a double-layer mixed structure, including a lower titanium oxide layer and an upper silicon oxide layer, and the sum of the optical thicknesses of the two is one-fourth of 850 nm.

[0033] Preferably, the n-type electrode layer 40 is AuGeNi / Au material with a total thickness of 300-500nm, and is located above and to the left of the n-type contact layer 30 ; the p-type electrode layer 100 is a TiAu bimetallic layer with a total thickness of 400-500nm, and is located above and to the left of the p-type contact layer 90 .

[0034] In the embodiment of the present invention, using Figure 2 The main steps of making the 850nm band high-responsivity detector from the epitaxial material shown are as follows:

[0035] Step 1: Figure 1 An isolation groove pattern is photoetched on the epitaxial material, and the epitaxial layer is etched through the aluminum oxide layer 20 to the n-type substrate 10 .

[0036] Step 2: Wet oxygen oxidation. The aluminum oxide layer 20 is laterally oxidized until it penetrates the entire layer. At this time, the aluminum oxide layer 20 becomes insulating aluminum oxide with a refractive index of about 1.75, which has a limiting effect on the current and isolates the device from the n-type substrate 10.

[0037] Step 3: grow an insulating layer and etch out an upper electrode window.

[0038] Step 4: Photolithography and metal stripping to form an N-type electrode.

[0039] Step 5: Photolithography and metal stripping to form a P-type electrode.

[0040] Step 6: Apply anti-reflection film.

[0041] Step 7: Wafer thinning and annealing.

[0042] The detector described in the embodiment of the present invention is obtained through the above process steps.

[0043] The above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A 850nm band high-responsivity detector, characterized by: It includes an n-type substrate located at the bottom of the detector, and the n-type substrate includes an aluminum oxide layer, an n-type contact layer, an n-type DBR layer, a lower limiting layer, an absorption layer, an upper limiting layer, a p-type contact layer and an anti-reflection film layer from bottom to top, and also includes an n-type electrode layer and a p-type electrode layer, the n-type electrode layer is located on the n-type contact layer and on one side of the n-type DBR layer, and the p-type electrode layer is located on the p-type contact layer and on one side of the anti-reflection film layer; The p-type contact layer is a p-type graded doping material with a total thickness of 110nm; the lower part is an AlGaAs graded layer, which is made of AlGaAs material with a gradually decreasing Al component from bottom to top until the upper GaAs contact surface, with a maximum Al component content of 0.3, which gradually decreases to 0.2, and a thickness of 100nm. The p-type doping concentration is 2x 10 17 / cm 3 Up to 1x 10 18 / cm 3 ; The thickness of the GaAs contact surface is 10nm, and the P-type doping concentration is 1x 10 19 / cm 3 ; The aluminum oxide layer is formed by growing AlAs or AlGaAs high aluminum-containing material on an n-type substrate during the device process and performing lateral wet oxygen oxidation. During the lateral wet oxygen oxidation, the aluminum oxide layer is a whole layer that penetrates laterally.

2. The 850nm band high-responsivity detector according to claim 1, characterized in that: The n-type substrate is made of GaAs material with ultra-low defect density and has a thickness of 80-150 μm.

3. The 850nm band high-responsivity detector according to claim 1, characterized in that: The aluminum oxide layer has an Al content greater than 98% and a thickness of 10-40 nm.

4. The 850nm band high-responsivity detector according to claim 1, characterized in that: The n-type doping concentration of the n-type contact layer is greater than 1x 10 18 / cm 3 , thickness is 30-100nm.

5. The 850nm band high-responsivity detector according to claim 1, characterized in that: The n-type DBR layer is a plurality of high / low aluminum component AlGaAs film pairs, each of which is composed of 850 / 4nm optical thickness high aluminum AlGaAs and 850 / 4nm optical thickness low aluminum AlGaAs, and the n-type doping concentration is 5x 10 17 / cm 3 Up to 1x 10 18 / cm 3 .

6. The 850nm band high-responsivity detector according to claim 5, characterized in that: The high aluminum AlGaAs is Al 0.7 GaAs, low aluminum AlGaAs is Al 0.1 GaAs, the total number of the thin film pairs is 10-20 pairs.

7. The 850nm band high-responsivity detector according to claim 1, characterized in that: The lower limiting layer is i-type AlGaAs material, Al component is 0.2-0.5, and thickness is 100-300nm; the absorption layer is i-type GaAs material, thickness is greater than 1μm; the upper limiting layer is i-type AlGaAs material, Al component is 0.2-0.5, and thickness is 100-300nm.

8. The 850nm band high-responsivity detector according to claim 1, characterized in that: The antireflection film layer is a double-layer mixed structure, including a lower titanium oxide layer and an upper silicon oxide layer, and the sum of their optical thicknesses is one quarter of 850 nm.

9. The 850nm band high-responsivity detector according to claim 1, characterized in that: The n-type electrode layer is made of AuGeNi / Au material with a total thickness of 300-500nm; the p-type electrode layer is a TiAu double metal layer with a total thickness of 400-500nm.

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