Studies on lasing and optical modes from GaN-based tubular microcavity fabricated by photoelectrochemical etching

Abstract

Ⅲ-nitride semiconductors have a wide range of emission spectrum from ultraviolet to infrared regime, and are promising materials for photonics research at room temperature due to their high exciton binding energy. As a representative optical resonator platforms based on Ⅲ-nitride semiconductors, microdisks and microrings have been studied in advance and new structures are also being carried out. In this work, a free-standing microtube structure consisting of Ⅲ-nitride semiconductors was realized and was demonstrated to be used as an optical resonator. After growing n-type GaN/InGaN/GaN/AlGaN on a sapphire substrate, removing GaN through photoelectrochemical etching turns the heterojunction layer of AlGaN/GaN into microtube structure by strain-induced self-rolling mechanism. The resonant modes (whispering gallery modes, WGMs) which is formed by total internal reflection along the circular shape of sidewall were observed through the photoluminescence measurement. Furthermore, it was experimentally confirmed that the polarization of WGMs was predominantly parallel to the tube axis. Also, lasing property was observed from the microtube using pulsed pumping laser. Additionally, InGaN/GaN single quantum well microtube was achieved and the resonant modes were observed, either. The group Ⅲ-nitride semiconductor-based microtube presented in this study are expected to be used as a new type of optical resonator in the field of photonics and further applied as a bio/chemical sensor.