Low-noise staircase, tunneling, and conventional avalanche photodetectors

Abstract

Many novel materials and device structures have been explored over the years in the quest for low-noise avalanche photodetectors (APD), which are attractive for a wide range of applications in imaging, communications, sensing, etc. This includes the introduction of heterojunctions to modify impact ionization rates [1], culminating in the proposal by Capasso et al. of a solid-state analog to the photomultiplier tube — the staircase APD [2]. In this device, band engineering and a small applied bias is used to form the conduction band into a series of steps, where impact ionization occurs deterministically as electrons cross each step. Unfortunately, the technologically-available materials at the time did not possess the necessary combination of large conduction band offset, small bandgap bottom step, and large Γ-L energy separation required to achieve true staircase operation.