Low Threshold GaInAsP Lasers with Semiconductor/Air Distributed Bragg Reflector Fabricated by Inductively Coupled Plasma Etching

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Abstract
We fabricated GaInAsP/InP short cavity lasers with semiconductor/air distributed Bragg reflectors (DBRs) by inductively coupled plasma etching with pure Cl2 gas. Nearly vertical sidewalls with low roughness of ∼10 nm were achieved, separated by air spaces of three quarter wavelengths. The lowest threshold current normalized by the stripe width was 3.2 mA/µm. From this value, the DBR reflectivity was evaluated to be 85%, which agreed with the theoretical value obtained from a finite-difference time domain (FDTD) simulation. We compared two types of devices with different DBR shapes, and observed that DBR reflectivity was affected more by the tilt of the DBR sidewalls than the sidewall roughness. This result also agreed well with the FDTD theory.