Work

Towards perpendicular and smooth sidewalls of pixels formed in III-V bulk and epitaxial materials used for IR detection

Year: 2025

Type: article

Abstract: • Investigation of ICP-RIE Etching: Examined the effects of Inductively Coupled Plasma-Reactive Ion Etching (ICP-RIE) on the morphology, sidewall slope, and surface roughness of GaSb homoepitaxial layer, GaSb bulk material, InAs bulk material and type II InAs/GaSb superlattice grown on GaSb substrate for infrared detection applications. • Optimization Across Power Regimes: Demonstrated how varying ICP-RIE power levels (40 W, 100 W, 200 W) influence etching outcomes, including etch rate, sidewall slope angle, and surface uniformity. • Material-Specific Insights: Identified that GaSb materials exhibited smoother and more stable sidewalls across all regimes compared to InAs-rich structures, which presented increased roughness and uneven sidewalls, particularly in superlattices. • Superlattice Challenges: Highlighted the etching complexities in type II InAs/GaSb superlattices due to interface instability between alternating layers, especially under high plasma power. This work reports on the effect of Inductively Coupled Plasma-Reactive Ion Etching (ICP-RIE) on the sidewalls of mesas formed in materials used in infrared detection: GaSb homoepitaxial layer, GaSb bulk material, InAs bulk material and type II InAs/GaSb superlattice grown on GaSb substrate. The influence of ICP-RIE power on the slope and morphology of mesa walls, and roughness of the top surface and around the pixels was examined. The ICP power was equal to the RIE power in particular etching processes. This paper presents the results for low (P = 40 W), medium (P = 100 W) and high-power (P = 200 W) etching conditions. The etching process was performed using a BCl 3 /Ar plasma at a temperature of about 23 °C, with a soft mask. The structures and surfaces were characterized using Scanning Electron Microscopy, an optical profilometer and Atomic Force Microscope. The roughness of top surface of mesa and area around it was evaluated. The etch rate and the angle of the sidewall slope were determined for pixels formed in investigated materials. The best results of etching were achieved using low-power and high-power ICP-RIE in a GaSb homoepitaxial material, which yielded smooth sidewalls with a slope angle of 85°.

Source: Applied Surface Science

DOI: 10.1016/j.apsusc.2025.162975