Investigation of Zn-diffusion in 2-micron InGaAs/GaAsSb superlattice planar diodes using atomic layer deposition of ZnO

Abstract

Sensing and imaging applications such as light detection and ranging (LiDAR) require a receiver with highly sensitive photodetectors such as avalanche photodiodes (APDs), which have high gain and speed. Conventionally, APDs use mesa structures that limit device scaling due to increased surface leakage current at smaller sizes. Planar-architectured APDs address high surface leakage current by reducing the exposed surface of the devices. They also eliminate complicated mesa fabrication steps such as mesa etching and passivation. Fabrication of APDs with planar architecture conventionally uses processes such as ion-implantation, which can damage the epitaxially-grown material, and metal organic chemical vapor deposition (MOCVD), which can be expensive and time-consuming. In this paper, we assess an alternative fabrication process to make APDs using Zn diffusion into epitaxially-grown material stacks through atomic layer deposition (ALD) of ZnO. In particular, we have explored Zn diffusion in epitaxially grown type-II InGaAs/GaAsSb superlattice on InP substrates. ZnO was grown with various thicknesses on the epitaxial stack using ALD, and the Zn was diffused into the stack using a diffusion furnace under forming gas. The effects of the diffusion process were investigated using various characterization techniques, including x-ray diffraction, and secondary ion mass spectroscopy. The optimized Zn-diffusion process is then used to make planar diodes. Further optimization of this diffusion process may lead to a rapid, manufacturable, and cost-effective method of developing planar APDs.