Stimulated emission and ultrafast carrier relaxation in InGaN multiple quantum wells

TL;DR

This study investigates stimulated emission and carrier relaxation in InGaN quantum wells, revealing how composition affects threshold power and relaxation mechanisms, with implications for laser design.

Contribution

It provides new insights into how In composition influences stimulated emission thresholds and carrier dynamics in InGaN quantum wells.

Findings

SE threshold power density increases with In composition.

Carrier capture occurs in less than 1 ps from barriers to QWs.

Higher In content introduces additional relaxation channels.

Abstract

Stimulated emission (SE) was measured from two InGaN multiple quantum well (MQW) laser structures with different In compositions. SE threshold power densities (I_th) increased with increasing QW depth (x). Time-resolved differential transmission measurements mapped the carrier relaxation mechanisms and explained the dependence of I_th on x. Carriers are captured from the barriers to the QWs in < 1 ps, while carrier recombination rates increased with increasing x. For excitation above I_th an additional, fast relaxation mechanism appears due to the loss of carriers in the barriers through a cascaded refilling of the QW state undergoing SE. The increased material inhomogeneity with increasing x provides additional relaxation channels outside the cascaded refilling process, removing carriers from the SE process and increasing I_th.