Decorrelation of internal quantum efficiency and lasing threshold in AlGaN-based separate confinement heterostructures for UV emission

TL;DR

This study investigates how carrier localization and diffusion affect the optical performance of AlGaN-based UV laser structures, revealing that improvements in carrier collection do not necessarily enhance internal quantum efficiency or reduce lasing threshold.

Contribution

It demonstrates that graded index structures improve carrier collection without increasing internal quantum efficiency, highlighting the complex relationship between localization and lasing performance.

Findings

Graded index structures enhance carrier collection at quantum wells.

Carrier localization increases radiative efficiency but not laser threshold.

Lasing threshold is more sensitive to carrier injection efficiency.

Abstract

In this paper, we study the internal quantum efficiency and lasing threshold of AlGaN/GaN separate confinement heterostructures designed for ultraviolet laser emission. We discuss the effect of carrier localization and carrier diffusion on the optical performance. The implementation of graded index separate confinement heterostructures results in an improved carrier collection at the multi-quantum well, which facilitates population inversion and reduces the lasing threshold. However, this improvement is not correlated with the internal quantum efficiency of the spontaneous emission. We show that carrier localization at alloy inhomogeneities results in an enhancement of the radiative efficiency but does not reduce the laser threshold, more sensitive to the carrier injection efficiency.