Trap-assisted tunneling in AlGaN avalanche photodiodes

Z G Shao,Q J Gu,H L Yu,X F Yang,J F Feng,X K Hong,J Zhang,D B Zhang,Y S Liu,Y W Kuang

doi:10.1063/1.4984214

Abstract

We fabricated AlGaN solar-blind avalanche photodiodes (APDs) that were based on separate absorption and multiplication (SAM) structures. It was determined experimentally that the dark current in these APDs is rapidly enhanced when the applied voltage exceeds 52 V. Theoretical analyses demonstrated that the breakdown voltage at 52 V is mainly related to the local trap-assisted tunneling effect. Because the dark current is mainly dependent on the trap states as a result of modification of the lifetimes of the electrons in the trap states, the tunneling processes can be modulated effectively by tuning the trap energy level, the trap density, and the tunnel mass.

Highlights

AlGaN avalanche photodiodes (APDs) have been attracting considerable interest because of their outstanding advantages, which include low operating voltages, low power consumption, small device size, and no requirement for cooling during operation.[1]
Use of AlGaN APDs could lead to relaxed system requirements for expensive filters because of their solar blind characteristics, and they represent perfect candidates to replace the current photomultiplier tubes, which are both bulky and fragile.[2]
Researchers are having great difficulty in realizing high-gain AlGaN APDs, which is mainly related to the growth of high-quality AlGaN layers on lattice-mismatched sapphire substrates and the high crystalline defect densities in the AlGaN and GaN layers

Summary

Introduction

AlGaN avalanche photodiodes (APDs) have been attracting considerable interest because of their outstanding advantages, which include low operating voltages, low power consumption, small device size, and no requirement for cooling during operation.[1]. Under high local electric fields, the tunneling of the electrons from the valence band to the conduction bands through traps or defects can obviously affect the avalanche processes.[12,13]

Results

Conclusion