單光子崩潰二極體之光子偵測特性

Abstract

在此論文中，我們使用台積電0.25-μm高壓標準CMOS製程製作的單光子崩潰二極體進行量測，詳細探討其光子偵測效率與jitter等光子偵測特性。在此工作中，和舊有的文獻相比，我們所量測的元件擁有較低的暗計數，此外，我們透過精準校正光量的方式，量測各元件在不同超額偏壓與入射光波長下的光偵測率，其最高偵測率在波長510 nm 時可達14.2%。藉由自動量測系統的建立，我們將光點縮小至約略1-μm，對元件主動區的光計數進行二維空間分佈量測，量測結果顯示，光計數在主動區內的二維分佈呈現環狀的不均勻現象，且在短波長及高偏壓下更為明顯，我們發現此現象和元件電極及其連接金屬的佈局有關，透過TCAD模擬，其結果顯示主動區電場呈現相同的環狀不均勻分佈，連帶使得光計數有相同的現象。另外，藉由脈衝雷射 (405 nm與782 nm) 與TCSPC卡的架設，我們可以在不同偏壓下對元件進行jitter量測與分析。最後，在相同的製程下，我們設計出兩個摻雜濃度類型相反的結構，並透過TCAD模擬來探討兩者的暫態響應，其結果有助於未來設計出低jitter的單光子崩潰二極體。

In this work, the photon detection performance of single-photon avalanche diodes (SPADs) fabricated in the high-voltage (HV) 0.25-μm CMOS technology is studied and discussed in details, including photon detection probability (PDE) and jitter. The devices measured in this work exhibited a very low dark count rate in a previous study. The wavelength-dependent PDEs are measured under various excess voltages. The maximun PDE of about 14.2% at 510 nm is obtained. By squeezing the incident light spot into about 1-μm, the 2-D spatial distribution of photo-counts in the circular active area are mapped automatically. The 2-D mappings of photo-counts reveal a clear ring-like non-uniformity. The non-uniform distribution becomes more significant with a shorter wavelength and a higher bias voltage. Simulations with TCAD are performed to understand the spatial distributions of electric field inside the active region. It is found that the arrangement of contact pad and connection metal line affects the electric field underneath, which results the non-uniformity of photo-counts. In addition, by using pulsed laser diodes at 405 and 782 nm and a time-correlated photon-counting card, the jitter distributions of the devices under various bias voltages are measured and analyzed. At last, by using the same technology, two new structures of SPADs with opposite doping types are designed and simulated to study their transient photo response, which would be helpful for achieving low jitter SPADs in the future.