一种低暗计数率P-I-N结构的单光子雪崩二极管探测器

A P-I-N Structure Single-Photon Avalanche Diode Detector with Low Dark Count Rate

基于180 nm BCD工艺制备出一种P型注入增强型P-I-N结构的单光子雪崩二极管(SPAD)探测器。采用P型漂移区与高压N+埋层之间的低掺杂浓度P型外延层作为I层深结雪崩区,提高了近红外波段的光子探测概率(PDP)。利用低掺杂浓度的P型外延层作为虚拟保护环,防止了器件横向击穿,降低了暗计数率(DCR)。测试结果表明,虚拟保护环宽度(GRW)为5μm时,器件雪崩电压为56 V。在5 V过偏压下600 nm处的峰值PDP为41%,在901 nm的近红外波段下PDP大于6%,DCR为0.56 s^(-1)·μm^(-2),后脉冲率小于1.2%,表现出良好的电学和光学特性。所提出的SPAD器件为硅基高灵敏度近红外单光子探测器设计提供了一种可选的解决方案。

Objective Over the past few decades,single-photon detection technology has rapidly developed.Single-photon avalanche diode(SPAD)detectors operating in Geiger mode have advantages such as high sensitivity,fast response speed,and strong capability for single-photon detection.As a result,they have been widely used in optical sensing fields such as quantum communication,lidar,and fluorescence lifetime imaging.SPAD arrays compatible with CMOS technology have gained significant attention due to their high integration and miniaturization.In laser radar applications,SPADs are employed to receive returning photons.However,optical signals are susceptible to environmental factors like dust and weather conditions.The received light intensity might be at the single-photon level,and high dark count noise can degrade device performance.Considering the potential harm of short-wavelength lasers to human eyes,the design of SPAD devices with low dark counts and high photon detection probabilities has become a hot research direction.Methods The SPAD(Fig.1)employs a P-I-N diode structure,with the avalanche region located between the P-type drift region and the high-voltage N+buried layer.The P epitaxial layer serves as the intrinsic region,with P-trap guard rings and virtual guard rings surrounding the P-doped region to mitigate the impact of shallow trench isolation on dark count rates(DCR).The proposed SPAD devices with GRW of 3,4,5μm are simulated based on 0.18μm BCD technology to study the impact of GRW on device performance[Fig.2(a)].Simulation results show that the device can only work normally at GRW of 5μm without a large edge electric field,and it will also cause the dark count to decrease.Figure 2(c)illustrates the 2D electric field distributions when STI extends into PW.Changing STI appropriately can hardly improve the electric field strength.Results and Discussions The I-V characteristic of the SPAD is firstly measured which exhibits avalanche breakdown voltage at around 56 V[Fig.3(c)],showing no difference to the TCAD simulation results(Fig.2).DCR measurement results[Fig.4(a)]show that the variation of DCR with Vex is not obvious and this value is more dependent on temperature changes.the data demonstrates excellent performance of 0.56 s^(-1)·μm^(-2)at 23℃and 5 V excess bias voltage.The PDP measurements(Fig.5)show that the peak PDP reaches 41.5%(600 nm)at Vex=5 V.Moreover,due to the wide depletion layer,there is a higher response sensitivity for near-infrared photons(780‒940 nm)and PDP at 905 nm is more than 6%.Conclusions We propose an additional P-type injection enhanced P-I-N structure SPAD based on the SMIC 180 nm BCD process.The test results show that at Vex=5 V,the PDP peak of the SPAD reaches 41.5%,and the near-infrared PDP at the 905 nm wavelength is larger than 6%.At room temperature,it achieves a median DCR of 0.56 s-1·μm-2 and a very low afterpulsing probability<1.2%when quenched passively with a dead time of 14μs.