Experimental observation of the linear gain of back-illuminated ultraviolet avalanche photodiodes using a GaN/AlN periodically stacked structure

Abstract

Semiconductor-based avalanche photodiodes (APDs) have the advantages of lower power and simpler fabrication of arrays compared with photomultiplier tubes. It is critical for weak-light imaging that the APD is operated under back illumination and with high linear gain. However, linear gain is fairly low for conventional PIN APDs. This paper presents a back-illuminated APD, whose multiplication layer is designed to be a GaN/AlN periodically stacked structure. The GaN/AlN heterostructure is introduced to enhance the ratio of ionization coefficient between electrons and holes, which proves to be helpful for increasing the linear gain. Under back illumination, the prototype device demonstrates a record-high external quantum efficiency (reflecting linear gain) of ∼5 × 102 at the reverse bias of 66 V. The device response spectra were also studied to further confirm that only the photo-excited electrons can trigger the collision ionization in the multiplication layer.

Role of impact ionization and self-consistent tunnel injection in Schottky-barrier diodes operating under strong reverse-bias conditions

“…In our case, a homemade Monte Carlo (MC) simulator coupled with a one-dimensional Poisson's solver will be used, which has already been successfully exploited for the simulation of SBDs. 25,26) Despite in some specifically designed devices, like avalanche photodiodes based on periodically stacked GaN/AlN structures, 27,28) II is unipolar (only provoked by electrons), in a general case hole-initiated II is also significant in GaN devices. [22][23][24]29) Theoretical studies indicate that holeinitiated II becomes dominant for field strengths of about 3.0 MV cm −1 , 30,31) attained in the devices we will analyze.…”