Special-shaped protection ring structure and implementation method of planar indium gallium arsenide linear detector

Abstract

The present invention discloses a special-shaped guard ring structure and implementation method for a planar indium gallium arsenide linear detector. The structure of the detector is designed as follows: a special-shaped guard ring is arranged on the linear detector, the diffusion holes of the guard ring are "comb-shaped" or "bow-shaped", surrounding three sides of each rectangular photosensitive element, and the P region of the guard ring and the N region of the device are merged and led out through an extended electrode. The implementation method is to obtain the diffusion holes of the photosensitive element and the diffusion holes of the guard ring synchronously by photolithography and etching on the N-InP / I-InGaAs / N-InP structure epitaxial material, perform P-type doping synchronously, and the extended electrode covers the P electrode hole of the guard ring and the N electrode groove of the device. The photo-generated carriers generated by the guard ring under light are led out through the extended electrode. The advantages of the present invention are as follows: this structure not only has the advantages of low dark current, high duty cycle, high detection rate, high reliability, etc. of a planar detector, but also effectively suppresses the problems of photosensitive element expansion caused by carrier lateral diffusion and crosstalk between adjacent photosensitive elements through the guard ring.

Description

Technical Field

[0001] The present invention relates to the technology of infrared photodetectors, specifically to a special-shaped protection ring structure and an implementation method of a planar indium gallium arsenide (InGaAs) linear array detector, which is applicable to the preparation of a front-illuminated InGaAs linear array detector with room-temperature operation, high detectivity, and low crosstalk. Background Art

[0002] In the field of infrared photodetectors, short-wave infrared InGaAs detectors have the advantages of uncooled room-temperature operation, high detectivity, and good uniformity in the wavelength band of 0.9μm - 1.7μm. They are beneficial to the realization of high-sensitivity, miniaturized, low-power, and highly reliable infrared detection systems, and have important applications in many fields such as space remote sensing, low-light-level night vision, and spectral detection.

[0003] Short-wave infrared InGaAs detectors adopt a photovoltaic photosensitive element structure, generally a PIN structure, and usually adopt the following two technical solutions: (1) Planar detectors are obtained by P-doping the surface N-type InP layer on N-InP / I-InGaAs / N-InP structural materials. The advantage of this method is that the PN junction of the device is buried in the InP layer, which reduces the difficulty of device passivation and makes the dark current and noise of the device relatively small. However, due to the lateral diffusion of carriers during the P-doping process, the photosensitive elements are enlarged, and crosstalk is likely to occur between adjacent photosensitive elements. Moreover, the enlargement of the photosensitive elements makes it difficult to define the photosensitive surface. (2) Mesa detectors are obtained by physically isolating the photosensitive elements through an etching process on in-situ doped P-InP / I-InGaAs / N-InP structural materials. The etched isolation grooves between adjacent photosensitive elements can effectively suppress the lateral diffusion of carriers, thereby reducing the crosstalk between adjacent photosensitive elements. However, because the mesa detectors have exposed sides, a passivation process is required to reduce the dark current of the device, and their detectivity is usually lower than that of planar detectors.

[0004] In response to the increasing requirements of infrared optoelectronic systems for the sensitivity of detectors, in order to obtain extremely low dark current and noise, adopting the planar technical solution has become the mainstream technical development direction of InGaAs detectors. Planar InGaAs detectors have the advantages of low dark current, high duty cycle, high detectivity, and high reliability, and InGaAs detectors also have the advantages of room-temperature operation and no need for cooling. In view of the phenomenon that the photosensitive elements of planar InGaAs detectors are enlarged and there is crosstalk between adjacent photosensitive elements, it is necessary to explore a new structure to solve this problem. Summary of the Invention

[0005] The present invention provides a special-shaped protection ring structure, which is applied to a front-illuminated InGaAs linear detector with photosensitive elements arranged in an "one-word" shape at equal intervals. While retaining the advantages of a planar detector such as low dark current, high duty cycle, high detectivity, and high reliability, it suppresses the crosstalk between adjacent photosensitive elements.

[0006] The present invention discloses a special-shaped protection ring structure for a planar InGaAs linear detector, which is characterized in that: there is a diffusion hole 1 on each photosensitive element, and a special-shaped protection ring is arranged on each detector. Its diffusion hole 2 is in a "comb shape" or "bow shape" and surrounds three sides of each photosensitive element. An N electrode groove 3 is arranged on each side of the linear array, a P electrode hole 4 is arranged on the diffusion hole 1 of each photosensitive element, and a row of protection ring P electrode holes 5 is arranged on the special-shaped protection ring, corresponding to the positions of the P electrode holes 4 of the photosensitive elements one by one. A P electrode 6 is led out from each P electrode hole 4 of the photosensitive element, and the extension electrode 7 of the detector covers the P electrode holes 5 of the special-shaped protection ring and the two N electrode grooves 3 of the device, and combines and leads out the P region of the special-shaped protection ring of the device and the N region of the detector.

[0007] The implementation method of the present invention is as follows: on the epitaxial material of the N-InP / I-InGaAs / N-InP structure, the diffusion hole 1 of the photosensitive element and the diffusion hole 2 of the protection ring are obtained through photolithography and etching. The surface N-type InP capping layer is P-doped through the diffusion holes, and the P region of the photosensitive element and the P region of the protection ring of the linear detector are obtained synchronously. After diffusion, a SiNx dielectric film is deposited on the surface of the detector, and then the N electrode groove 3, the P electrode hole 4 of the photosensitive element, and the P electrode hole 5 of the special-shaped protection ring are obtained through photolithography and etching respectively. Metal electrodes are deposited to obtain the P electrode 6 of the photosensitive element and the extension electrode 7. This extension electrode conducts the P region of the protection ring and the N region of the device, and the photo-generated carriers generated by the protection ring under illumination are led out through the N electrode.

[0008] The advantages of the present invention are as follows:

[0009] 1. The planar diffusion process buries the PN junction of the photosensitive element in the InP layer, without considering the side passivation problem of the PN junction, effectively suppressing the dark current and noise of the device;

[0010] 2. The special-shaped protection ring and the photosensitive element are opened and diffused synchronously, and the process is simple;

[0011] 3. The P region of the special-shaped protection ring and the N region of the device are directly conducted through the extension electrode, and the photo-generated carriers generated by the protection ring under illumination are led out through this electrode, effectively isolating the crosstalk between adjacent photosensitive elements;

[0012] 4. The structure of the present invention is simple and applicable to front-illuminated linear detectors of different scales and different photosensitive element sizes. Description of the Drawings

[0013] Figure 1Schematic diagram of diffusion holes of InGaAs linear detector with special-shaped protection ring;

[0014] In the figure: 1 - Diffusion hole of photosensitive element;

[0015] 2 - Diffusion hole of protection ring;

[0016] Figure 2 Schematic diagram of electrode holes and electrodes of InGaAs linear detector with comb-shaped protection ring;

[0017] In the figure: 3 - N electrode groove;

[0018] 4 - P electrode hole of photosensitive element;

[0019] 5 - P electrode hole of protection ring;

[0020] Figure 3 Front top view of InGaAs linear detector with special-shaped protection ring;

[0021] In the figure: 6 - P electrode of photosensitive element;

[0022] 7 - Extended electrode. Specific implementation mode

[0023] The following further elaborates on the specific implementation mode of the present invention in conjunction with the attached drawings.

[0024] This embodiment is a planar InGaAs linear detector with a "comb-shaped" protection ring structure of 10×1 element.

[0025] Molecular beam epitaxy (MBE) is used to grow epitaxial materials. On an N-type InP substrate with a thickness of 350 μm, a diameter of 2 inches, and a carrier concentration of 3×10 18 cm -3 , an N-type InP buffer layer with a thickness of 1 μm and a carrier concentration of 3×10 18 cm -3 is successively grown; an intrinsic InGaAs absorption layer with a thickness of 2.5 μm and a carrier concentration of 1×10 16 cm -3 ; an N-type InP cap layer with a thickness of 1 μm and a carrier concentration of 5×10 16 cm -3 .

[0026] A 300-nm-thick SiNx diffusion mask layer is grown on the surface of the epitaxial material by plasma-enhanced chemical vapor deposition (PECVD). According to Figure 1As shown, the photosensitive element diffusion holes 1 and the comb-shaped guard ring diffusion holes 2 are obtained through positive photoresist lithography and reactive ion etching (RIE). The line array scale of the photosensitive elements is 10×1. The photosensitive elements are rectangular structures. The photosensitive element diffusion hole 1 is an inverted "convex" hole, with the upper large hole being 84μm×100μm and the lower small hole being 40μm×40μm. The guard ring surrounds three sides of each photosensitive element in a "comb" shape. The width of the comb handle part of the guard ring diffusion hole 2 is 40μm, the width of the comb tooth part is 4μm, the width of the non-diffusion area between the comb teeth and the photosensitive element diffusion hole is 6μm, and the center distance between adjacent photosensitive elements is 100μm.

[0027] The epitaxial material and the Zn3P2 doping source are sealed together in a high-vacuum quartz tube, and the sample is diffused at 530°C for 10 minutes to form the photosensitive element P region and the guard ring P region. A SiNx passivation layer with a thickness of 300nm is deposited on the chip surface by PECVD. Then, through positive photoresist lithography, RIE etching of the passivation layer, and ICP etching of the N electrode groove, the passivation layer, the diffusion mask layer, the cap layer InP cap layer, and the intrinsic InGaAs absorption layer in the selected area are etched away, entering the InP buffer layer region to obtain the device N electrode groove 3 with a depth of 4.3μm - 4.5μm and a width of 60μm. Through positive photoresist lithography and RIE etching, the photosensitive element P electrode hole 4 and the guard ring P electrode hole 5 are obtained. The size of 4 is 30μm×30μm, and the size of 5 is 20μm×20μm, as shown in Figure 2 shown. Through positive photoresist lithography, a single layer of Au with a thickness of 200nm is evaporated by electron beam evaporation to obtain the photosensitive element P electrode 6 and the extended electrode 7, as shown in Figure 3 shown. Among them, the photosensitive element P electrode 6 covers the small hole in the photosensitive element diffusion region, with a size of 80μm×280μm, and is extended and led out on one side for easy wire bonding. The extended electrode 7 is a special-shaped structure that covers the N electrode groove 3 and the guard ring electrode hole 5, directly conducts the guard ring P region and the device N region, and the width of the comb-shaped electrode connected to the guard ring P electrode hole 5 is 25μm, and the width of the remaining area is more than 80μm.

[0028] Using acetone floating glue, ethanol cleaning, and nitrogen drying, the 10-element planar InGaAs linear detector with a comb-shaped guard ring is fabricated.

Claims

1. An abnormal protection ring structure for a planar indium gallium arsenide linear detector. The detector is a front-illuminated device with photosensitive elements arranged in an "one-word" pattern at equal intervals. It is characterized in that: Each photosensitive element on the indium gallium arsenide linear array detector has a photosensitive element diffusion hole (1). An irregular-shaped guard ring is provided on each detector, and its guard ring diffusion hole (2) is "comb-shaped", surrounding three sides of each photosensitive element. An N electrode groove (3) is provided on each side. A photosensitive element P electrode hole (4) is provided on each photosensitive element diffusion hole (1). A row of guard ring P electrode holes (5) is provided on the irregular-shaped guard ring, and the position of each guard ring P electrode hole (5) corresponds one-to-one with the position of the corresponding photosensitive element P electrode hole (4). After forming the diffusion hole (1) of the photosensitive element and the diffusion hole (2) of the irregular-shaped guard ring, the photosensitive element P region and the irregular-shaped guard ring P region are formed by diffusing the N-InP / I-InGaAs / N-InP structure. The photosensitive element diffusion hole (1) is an inverted "convex" hole, and the photosensitive element diffusion hole (1) includes an upper large hole and a lower small hole. The photosensitive element P electrode hole (4) is located in the lower small hole. A P electrode (6) is led out from each photosensitive element P electrode hole (4). The extension electrode (7) of the detector covers the guard ring P electrode hole (5) of the irregular-shaped guard ring and the two N electrode grooves (3) of the device, and leads out by combining the irregular-shaped guard ring P region of the device with the detector N region.

2. A method for implementing the abnormal protection ring structure of the planar indium gallium arsenide linear detector according to claim 1, characterized in that The implementation method is as follows: On the epitaxial material of the N-InP / I-InGaAs / N-InP structure, the photosensitive element diffusion hole (1) and the guard ring diffusion hole (2) are obtained through photolithography and etching. The surface N-type InP capping layer is P-doped through the diffusion holes, and the photosensitive element P region and the guard ring P region of the linear array detector are obtained synchronously. After diffusion, a layer of SiNx dielectric film is deposited on the detector surface, and then the N electrode groove (3), the photosensitive element P electrode hole (4), and the irregular-shaped guard ring P electrode hole (5) are obtained through photolithography and etching respectively. Metal electrodes are deposited to obtain the photosensitive element P electrode (6) and the extension electrode (7). This extension electrode conducts the guard ring P region and the device N region, and the photo-generated carriers generated by the guard ring under illumination are led out through the N electrode.

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