The Effect of Inductively Coupled Plasma Etching on the I–V Curves of the Avalanche Photodiode with GaN/AlN Periodically Stacked Structure

Abstract

Inductively coupled plasma (ICP) is widely used in dry etching of III‐nitride materials, wherein the etching parameters of GaN and AlN are very different. Herein, the ICP dry etching process parameters of GaN/AlN periodically stacked structure (PSS) for avalanche photodiode (APD) fabrication are intensively studied and optimized. The flow rate ratio of Cl2/BCl3/Ar plasma, bias voltage, and the GaN‐to‐SiNx selectivity of ICP etching are optimized to achieve excellent surface morphology and nearly vertical sidewalls. It is found that the etching rate and the etched surface roughness of GaN/AlN material are significantly influenced by the flow rate of Cl2. After optimizing the etching procedure, the root‐mean‐square roughness of the etched surface is measured to be 1.46 nm, which is close to the as grown surface. By using the optimized ICP dry etching in the fabrication of the GaN/AlN PSS APD, the dark current is suppressed from 3.6 to 8.2 × 10−3 A cm−2 at −90 V.