The influence of quantum-well composition on the performance of quantum dot lasers using InAs-InGaAs dots-in-a-well (DWELL) structures

TLDR

The study investigates how the number of dots‑in‑a‑well layers and the indium composition of the surrounding InGaAs quantum well affect the optical performance of quantum dot lasers. The authors compare 1‑DWELL and 3‑DWELL lasers with InGaAs QWs containing 10–20 % indium to a conventional strained In₀.₁₅Ga₀.₈₅As QW laser, measuring internal quantum efficiency, modal gain, and characteristic temperature while keeping the dot density constant. 1‑DWELL lasers reach a threshold current density of 16 A/cm², 7.5 times lower than a conventional QW device, and both internal quantum efficiency and modal gain improve with deeper QWs and more DWELL layers; higher indium content further raises the characteristic temperature and maximum modal gain, showing that the surrounding QW is essential for efficient DWELL lasers.

Abstract

The optical performance of quantum dot lasers with different dots-in-a-well (DWELL) structures is studied as a function of the well number and the indium composition in the InGaAs quantum well (QW) surrounding the dots. While keeping the InAs quantum dot density nearly constant, the internal quantum efficiency /spl eta//sub i/, modal gain, and characteristic temperature of 1-DWELL and 3-DWELL lasers with QW indium compositions from 10 to 20% are analyzed. Comparisons between the DWELL lasers and a conventional In/sub 0.15/Ga/sub 0.85/As strained QW laser are also made. A threshold current density as low as 16 A/cm/sup 2/ is achieved in a 1-DWELL laser, whereas the QW device has a threshold 7.5 times larger. It is found that /spl eta//sub i/ and the modal gain of the DWELL structure are significantly influenced by the quantum-well depth and the number of DWELL layers. The characteristic temperature T/sub 0/ and the maximum modal gain of the ground-state of the DWELL structure are found to improve with increasing indium in the QW It is inferred from the results that the QW around the dots is necessary to improve the DWELL laser's /spl eta//sub i/ for the dot densities studied.