窒化物材料系テラへルッ帯量子力スケードレーザーの開発

摘要

This paper reviews recent progress in terahertz-quantum cascade lasers (THz-QCLs) using III-Nitride semiconductors, which are promising materials for the expansion of the operational frequency range (5-12 THz) on THz-QCLs, because these compounds have much higher longitudinal optical phonon energies (> 18 THz) than those of conventional GaAs-based materials (～9 THz). We designed a resonant phonon type GaN/(In)A1GaN QC structure that emits in the THz range and confirmed in GaN-based QCLs that population inversion can be obtained with numerical calculations based on the self-consistent rate equation model. We successfully fabricated GaN-based QC heterostructures with one-monolayer-thick accuracy by introducing droplet elimination by a thermal annealing (DETA) technique in molecular-beam epitaxy. Moreover, for the first time, we successfully observed spontaneous intersubband emissions in the THz range from GaN-based QCL structures. In this paper, we demonstrate recent achievements on the quantum design, fabrication technique, and electroluminescence properties of GaN-based QCL structures.