| 摘要: | 三五族單光子崩潰二極體(Single-Photon avalanche Diode, SPAD) 能夠偵測到近紅外光並具有單光子偵測的能力，因此被廣泛應用在醫療、軍事、量子通訊、車用安全等。以車輛安全系統為例，元件做為Time of flight (TOF) 接收器，其光子偵測效率和時間特性直接影響車用系統的安全距離判斷精確率，因此本研究針對吸收層加入部分摻雜之特殊設計降低載子在元件內部漂移時間以改善元件時間特性，並改進元件製程來降低暗計數。
我們的砷化銦鎵/砷化銦鋁SPAD被製作成圓形檯面，以提供側向電場限制並避免邊緣擊穿，我們研究了不同的蝕刻溶液，以改善側壁的粗糙度，從而減少表面缺陷。我們在蝕刻後進一步採用了硫化工藝以修復表面缺陷，這有助於減少器件的洩漏電流。最後，在器件上沉積了SixNy層作為鈍化層，以保護器件並保持硫化效果。
我們的SPAD的崩潰電壓在275K時為32.84 V，溫度係數為10.53 mV / K，在90%崩潰電壓之下漏電流為1.236×10−3 (A/cm2) ，其中已優化蝕刻液元件的漏電流比未優化蝕刻液的漏電流低3個數量級，僅比乾蝕刻高1個數量級。在237.5 K的溫度下測得的最低暗計數率為17％，SPAD的最短延遲時間約為120 ns，其中後脈衝率小於1％。但是，在這樣的溫度下，我們的SPAD表現出極低的光子靈敏度。當溫度升高到287.5 K時，暗計數率為26％，光子檢測效率為1.4％在過量偏壓為1.5％時。在室溫下過量偏壓為2％時，時間特性（也稱為抖動）達到164ps。
;III-V Single-photon avalanche diode (SPAD) can detect near-infrared light and have the ability of single-photon detection. Therefore, it is widely used in medical, military, quantum communications, vehicle safety, etc. Taking the vehicle safety system as an example, the SPAD device is used as a time of flight (TOF) receiver. The photon detection efficiency and timing performance directly affect the accuracy of the safety distance judgment of the vehicle system. Therefore, this study focuses on improving timing performance by introducing partially doped region to the absorption layer. Such design reduces carrier drift time inside the device structure so as to improve timing performance. At the same time, we also fabricate the device with delicate process for reducing dark count rate.
lateral electric field confinement as well as to avoid the edge breakdown. We examine different etching solutions to improve the roughness of the side walls and hence to reduce the surface defects. We further incorporate the vulcanization process after etching to fix the surface defects, which helps to reduce the leakage current of the device. Finally, A SixNy layer was deposited on the device as a passivation layer to protect the device and maintain the vulcanization effect.
The breakdown voltage of our SPAD is 32.84 V at 275K and the temperature coefficient is 10.53 mV/K. The leakage current is 1.236×10−3 (A/cm2) at 90% breakdown voltage, where the leakage current of optimized device is 3 orders of magnitude lower than that of without optimizing the etching solution, and it is only 1 order of magnitude higher than that using dry etching. The lowest dark count probability of 17 % was measured at the temperature of 237.5K. The III shortest hold-off time for our SPAD is around 120 ns where the afterpulsing probability is less than 1 %. However, at such temperature, our SPAD exhibits extremely low photon sensitivity. When the temperature is increased to 287.5K, the dark count probability is 26% and the photon detection efficiency is 1.5% for the excess bias of 1.4%. The timing performance, which is also known as jitter, reaches 164ps when the excess bias is 2% at room temperature. |
