GaAs–Al<i>x</i>Ga1−<i>x</i>As Double Heterostructure Injection Lasers

TLDR

Double heterostructure GaAs–AlxGa1−xAs junction lasers with very low thresholds and continuous operation above room temperature were fabricated by liquid phase epitaxy. The lasers exhibit a linearly decreasing threshold current density with active‑region thickness (3 → 0.5 µm), near‑perfect carrier and optical confinement from large band‑gap and index steps, superlinear gain versus current density, loss close to free‑carrier limits, and complete TE‑mode polarization due to enhanced reflection.

Abstract

Double heterostructure GaAs–AlxGa1−xAs junction lasers which have very low thresholds and which have been operated continuously at and above room temperature have been fabricated by liquid phase epitaxial growth. The threshold current density of these lasers decreases approximately linearly with the thickness of the active region from 3 to at least 0.5 μm. This is interpreted as the result of near perfect carrier and optical confinement as the result of large steps in the energy gap and index of refraction at the heterojunctions in these diodes. The gain in these lasers is very high and its dependence upon current density is superlinear. Loss is very low and almost that expected from free carriers. Complete polarization of the lasing mode was observed. This latter is interpreted to be the result of an increased reflection coefficient for the T E mode.