Reduction of the lasing threshold in optically pumped AlGaN/GaN lasers with two-step etched facets

TL;DR

This paper introduces a two-step etching process to create smooth, vertical facets in AlGaN/GaN UV lasers, significantly reducing the lasing threshold and enhancing optical performance compared to traditional methods.

Contribution

The study presents a novel two-step etching technique combining dry and wet etching to improve facet quality and laser performance in UV AlGaN/GaN lasers.

Findings

Lasing threshold reduced to nearly half with the new process

Facets are smooth, vertical, and parallel due to anisotropic wet etching

Optical performance is significantly improved over mechanical cleaving methods

Abstract

We report a two-step process to obtain smooth and vertical {10-10} m-plane facets in AlGaN/GaN separate confinement heterostructures designed to fabricate UV lasers emitting at 355 nm. The process consists in a dry etching by RIE-ICP combined with a crystallographic-selective wet etching process using a KOH-based solution. The anisotropy in the wet etching rates between the different crystallographic planes of the AlGaN structure, allows the fabrication of flat and parallel facets without a degradation of the multilayered ensemble. The optical performance of the lasers display a major improved when using the two-step process for the definition of the cavity, in comparison to cavities fabricated by mechanical cleaving, with the lasing threshold under optical pumping being reduced to almost half.