Single photon avalanche diode structure integrated with active quenching device

Abstract

The utility model discloses a single photon avalanche diode structure integrated with an active quenching device, and belongs to the technical field of semiconductor photoelectrons. The structure comprises an InP substrate, an InP buffer layer, an InGaAs absorption layer, an InGaAsP gradient layer, an InP charge layer integrated with an active quenching device, an InP cap layer, a SiN dielectric layer, an N electrode and a P electrode. The device is a positive irradiation single photon avalanche diode. Wherein the InP cap layer is integrated with a metal-insulator-semiconductor field effect transistor (MISFET), and the drain electrode of the field effect transistor and the P electrode of the InGaAs / InP single photon avalanche diode share a diffusion region. According to the utility model, the passive quenching and active recovery functions of the single photon avalanche diode are realized, and an active quenching device is integrated on the InP cap layer, so that parasitic parameters introduced in a circuit connection process are reduced, and therefore, avalanche charges of the avalanche diode can be reduced, and post-pulses can be suppressed. And the integration mode can be based on a manufacturing process of a standard single photon avalanche diode, and integration can be realized by only adding a photoetching step.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor optoelectronics, in particular to a single-photon avalanche diode structure with an integrated active quenching device. The diode can work in a passive quenching active recovery mode. Technical Background

[0002] At present, InGaAs single-photon avalanche diodes that respond to the 1550nm communication band have great application prospects in the fields of laser radar detection, three-dimensional imaging, laser communication, etc. Avalanche diodes that use the principle of collision ionization to realize single-photon detection function work above the breakdown voltage. This mode is called the Geiger mode. The diodes that are triggered by carriers to self-sustaining avalanches need to be quenched in time after completing the detection function, reducing the voltage across the diode to below the breakdown level, and quickly recovering to the state to be detected, waiting for the next photon to trigger the avalanche again. Especially for weak light detection application scenarios such as laser radar where the arrival time of photons is random, single-photon avalanche diodes need to work in free-running mode.

[0003] However, the existing solutions for achieving free operation have the following defects:

[0004] 1. Passive quenching recovery Due to the short time constant caused by the huge series resistance, the single-photon avalanche diode has a long recovery time, resulting in low maximum detection efficiency of the device.

[0005] 2. Connecting the quenching recovery element by means of leads will cause large parasitic capacitance, which will lead to a larger avalanche current when the device is working, causing serious after-pulse effects in the device, and the resulting error counts will interfere with the normal operation of the device.

[0006] Existing research reports: Due to the difference in parasitic capacitance, the solution of actively quenching and recovering components in chip interconnection can achieve lower avalanche current than the method of connecting discrete devices. In order to further reduce the avalanche charge, the active quenching and recovery components are directly connected to the single-photon avalanche diode in an on-chip integrated manner to minimize the parasitic parameters. To this end, this invention invents a new device structure from the perspective of device design to achieve passive quenching and active recovery of single-photon avalanche diodes, and integrates active quenching devices in the cap layer of single-photon avalanche diodes to reduce parasitic parameters during passive quenching and active recovery, which can effectively suppress the after-pulse effect and improve the single-photon detection level of the avalanche diode. Utility Model Content

[0007] In order to overcome the deficiencies of the prior art, the utility model provides a single-photon avalanche diode structure with an integrated active quenching device.

[0008] One of the purposes of the utility model is to integrate an active quenching device in the cap layer of an InGaAs / InP single-photon avalanche diode, thereby minimizing the parasitic parameters of the connected quenching recovery element, suppressing the after-pulse effect caused by a large avalanche current, and optimizing the detection performance of the single-photon avalanche diode.

[0009] The second purpose of the utility model is to realize the active recovery of the passive quenching of the InGaAs / InP single-photon avalanche diode, which can shorten the recovery time during the Geiger mode operation, increase the maximum counting rate of the device, and optimize the detection performance of the single-photon avalanche diode.

[0010] One of the purposes of the utility model is achieved by the following technical solution:

[0011] A single-photon avalanche diode structure with an integrated active quenching device comprises: a substrate, a buffer layer, an absorption layer, a gradient layer, a charge layer and a cap layer of the integrated active quenching device, characterized in that: the diode is a positive illumination type photodiode, and the photosensitive surface is located in the central area of ​​the diode cap layer surface; the upper layer of the substrate is an InP buffer layer, an InGaAs absorption layer, an InGaAsP gradient layer, an InP charge layer and an InP cap layer of an integrated transistor in sequence; a two-step stepped P-type diffusion region is designed at the central position of the upper part of the cap layer, a single-step annular P-type diffusion region is arranged in the outer ring of the stepped P-type diffusion region, a diode P electrode is led out from the top of the stepped P-type diffusion region, the stepped P-type diffusion region serves as a common electrode for the diode P pole and the integrated transistor, the single-step annular P-type diffusion region leads out the source of the integrated transistor, a dielectric film is grown above the annular area between the two diffusion regions of the cap layer, a metal is grown above the dielectric film as the gate of the integrated transistor, an N groove is opened downward in the InP cap layer, and the N groove passes through the InGaAs absorption layer.

[0012] The single-photon avalanche diode structure with integrated active quenching device is characterized in that a field effect transistor is integrated into the avalanche diode cap layer as an active quenching device.

[0013] The single-photon avalanche diode structure with integrated active quenching device is characterized in that the stepped P-type diffusion region of the cap layer is a diffusion well structure in which the transistor source and the single-photon avalanche diode P electrode share a common structure.

[0014] The single-photon avalanche diode structure with integrated active quenching device is characterized in that there is an annular P-type diffusion region outside the stepped P-type diffusion region in the center of the cap layer, a part of the annular P-type diffusion region serves as the drain of the field effect transistor, and the annular part serves as a protection ring of the single-photon avalanche diode.

[0015] The single-photon avalanche diode structure with integrated active quenching device is characterized in that an insulating dielectric film is grown on the InP cap layer after diffusion.

[0016] The single-photon avalanche diode structure with integrated active quenching device is characterized in that a layer of metal is grown on the surface of the insulating dielectric film as the gate metal material of the field effect transistor, and the pattern of the metal film is limited to the position between the annular diffusion area and the step-type area, and does not cover the diffusion area.

[0017] The single-photon avalanche diode structure with integrated active quenching device is characterized in that thickened electrode lead-out pads are grown on the surfaces of the gate, source and drain of the field effect transistor, and thickened electrodes are grown on the surface of the N groove of the InP cap layer.

[0018] The second purpose of the utility model is achieved by the following technical solution:

[0019] The designed diode structure can realize passive quenching and active recovery operation mode.

[0020] Furthermore, the integrated field-effect transistor is used to realize the passive quenching active recovery of the single-photon avalanche diode.

[0021] Furthermore, the passive quenching and active recovery operation scheme is: add a DC bias to the diode P-pole and the transistor source to above the transistor breakdown voltage, the field effect transistor gate voltage is at a low level, the source and drain are almost not conducting, and act as a huge resistor. When an avalanche occurs, the source and drain quickly divide the voltage across the diode to quickly quench the diode. After a period of time, the carriers captured by the diode trap are fully released, the field effect transistor gate level is set to a high level, and the source and drain are instantly turned on to recharge the diode to a detectable state.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. Integrate the field effect transistor in the InP cap layer and use it as an integrated active quenching device to achieve passive quenching and active recovery of the device.

[0024] 2. By integrating active quenching devices, the parasitic parameters introduced by the circuit leads can be eliminated to the greatest extent, which can reduce the avalanche current of the single-photon avalanche diode, suppress the after-pulse effect, and improve the detection performance of the single-photon avalanche diode.

[0025] 3. The utility model can be based on the process flow of the standard InGaAs / InP single-photon avalanche diode, and the preparation of the structure can be achieved by adding only one photolithography process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0027] Figure 1It is a cross-sectional view of the device structure of the utility model;

[0028] Figure 2 It is a cross-sectional view of the device cap layer integrated active device of the utility model;

[0029] Figure 3 A schematic diagram of the definition of electrodes derived from the cap layer of the device of the utility model;

[0030] Figure 4 A top view of the device of the utility model;

[0031] Figure 5 It is the equivalent circuit diagram of the device of the utility model;

[0032] Figure 6 This is the equivalent circuit diagram of active recovery and recharging during the utility model. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. It should be noted that the drawings of the utility model are all simplified and use non-precise proportions, which are only used for convenience and to clearly assist in explaining the purpose of the embodiments of the utility model. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0034] like Figure 1 As shown, the utility model provides a single-photon avalanche diode structure with an integrated active quenching device, the structure comprising an InP substrate 16, an InP buffer layer 1; an InGaAs absorption layer 2; an InGaAsP gradient layer 3; an InP charge layer 4; an InP cap layer 5; an N groove 6; an annular P-type diffusion region 7, which is used as a guard ring of the single-photon avalanche diode and a source of a field effect transistor; an annular diffusion region 8, which is used as a guard ring of the single-photon avalanche diode; a step-shaped P-type diffusion region 9 formed by two-step diffusion, which is used as a P-pole of the diode and a common drain of the field effect transistor; an insulating dielectric film 10; a gate 11 of the field effect transistor; a thickened electrode 12 arranged on the source of the field effect transistor; a thickened electrode 13 grown on the gate of the field effect transistor; a thickened electrode 14 arranged on the P-pole of the diode and the common drain of the field effect transistor; and an N electrode 15.

[0035] The utility model is based on an InGaAs single-photon avalanche diode chip with a separated absorption, gradient, charge, and multiplication (SAGCM) epitaxial structure, and integrates a metal-insulator-semiconductor field-effect transistor (MISFET) in an InP cap layer to realize passive quenching and active recovery of the single-photon avalanche diode, thereby reducing the recovery time in the process of detecting photons with random arrival times, and the structure has small parasitic parameters and can effectively suppress the after-pulse of the avalanche diode.

[0036] In one embodiment, the specific steps of preparing the InP cap layer are:

[0037] 1. Deposition of silicon nitride diffusion mask,

[0038] 2. Open the first diffusion window,

[0039] 3. Closed tube diffusion,

[0040] 4. Open the second diffusion window,

[0041] 5. Closed tube diffusion,

[0042] 6. Open N slots,

[0043] 7. Deposition of silicon nitride dielectric film,

[0044] 8.Grow gate metal,

[0045] 9. Open P (drain), N, gate, and source electrode holes,

[0046] 10. Grow and thicken the electrode.

[0047] In one embodiment, the equivalent circuit of the designed device realizing passive quenching active recovery in Geiger mode is as follows: Figure 5 , Figure 6As shown, when the single-photon avalanche diode is working, the diode is biased to above the breakdown voltage, and a modulation pulse is applied to the gate of the field effect transistor, which is in the off state of the low-level field effect transistor. When the device avalanche is triggered, the single-photon avalanche diode is charged. Since the field effect transistor is in the off state, it is similar to the avalanche diode connected in series with a large voltage divider resistor. The avalanche instantly divides the voltage across the single-photon avalanche diode, the avalanche diode junction capacitance is discharged, and the single-photon avalanche diode is quickly quenched. After a period of dead time, that is, waiting for the trapped carriers in the diode to be released, the gate modulation signal turns to a high level at this moment, turning on the source and drain of the field effect transistor, and recharging the junction capacitance of the single-photon avalanche diode to a bias above the breakdown voltage, so that the diode quickly recovers to the state where photons can be detected. The single-photon avalanche diode designed in the utility model utilizes an integrated MISFET as an active recovery element, shortens the recovery time of traditional passive quenching, and significantly reduces the parasitic capacitance of the active recovery circuit, thereby reducing the amount of avalanche charge, thereby suppressing the after-pulse effect, and improving the single-photon detection performance of the avalanche diode.

[0048] The above-mentioned implementation modes are only preferred implementation modes of the present invention, and cannot be used to limit the protection scope of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A single photon avalanche diode structure with an integrated active quenching device, comprising: The invention discloses a substrate, a buffer layer, an absorption layer, a gradient layer, a charge layer and a cap layer of an integrated active quenching device, wherein the diode is a positive illumination type photodiode, and the photosensitive surface is located in the central area of ​​the diode cap layer surface; the upper layer of the substrate is an InP buffer layer, an InGaAs absorption layer, an InGaAsP gradient layer, an InP charge layer and an InP cap layer of an integrated transistor in sequence; a two-step stepped P-type diffusion region is designed at the central position of the upper part of the cap layer, a single-step annular P-type diffusion region is arranged in the outer ring of the stepped P-type diffusion region, a diode P electrode is led out from the top of the stepped P-type diffusion region, the stepped P-type diffusion region serves as a common electrode for the diode P pole and the integrated transistor, the single-step annular P-type diffusion region leads out the source of the integrated transistor, a dielectric film is grown above the annular area between the two diffusion regions of the cap layer, a metal is grown above the dielectric film as the gate of the integrated transistor, an N groove is opened downward in the InP cap layer, and the N groove passes through the InGaAs absorption layer.

2. The single photon avalanche diode structure with integrated active quenching device according to claim 1, characterized in that: The field effect transistor is integrated into the avalanche diode cap layer as an active quenching device.

3. The single photon avalanche diode structure with integrated active quenching device according to claim 2, characterized in that: The stepped P-type diffusion region of the cap layer is a diffusion well structure in which the transistor source and the single-photon avalanche diode P electrode share a common structure.

4. The single photon avalanche diode structure with integrated active quenching device according to claim 3, characterized in that: There is an annular P-type diffusion region around the stepped P-type diffusion region in the center of the cap layer. A part of the annular P-type diffusion region serves as a drain of the field effect transistor, and the annular part serves as a protection ring of the single photon avalanche diode.

5. The single photon avalanche diode structure with integrated active quenching device according to claim 4, characterized in that: After the InP cap layer is diffused, an insulating dielectric film is grown.

6. The single photon avalanche diode structure with integrated active quenching device according to claim 5, characterized in that: A layer of metal is grown on the surface of the insulating dielectric film as a gate metal material of the field effect transistor. The pattern of the metal film is limited to a position between the annular diffusion region and the step-type region and does not cover the diffusion region.

7. The single photon avalanche diode structure with integrated active quenching device according to claim 6, characterized in that: Thickened electrodes are grown on the surfaces of the gate, source and drain of the field effect transistor to lead out pads, and thickened electrodes are grown on the surface of the N groove of the InP cap layer.

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