Low-threshold disorder-defined buried-heterostructure AlxGa1−xAs-GaAs quantum well lasers

Abstract

Two different quantum well heterostructure wafers are used to fabricate buried-heterostructure AlxGa1−xAs-GaAs quantum well lasers using Si-induced layer disordering (via Si diffusion). In contrast to the first wafer (QWH1), the second quantum well wafer (QWH2) utilizes Zn instead of Mg as the p-type dopant in the top AlxGa1−xAs confining layer and yields, because of concentration mismatch in acceptor and donor doping in the confining layers (nZn>nSe), inferior laser diodes owing to Zn diffusion from the p-type to the n-type confining layer during high temperature processing (850 °C Si diffusion). The first quantum well heterostructure, however, employs a lower concentration Mg doping for its p-type confining layer (nMg<nSe) and yields high performance devices when used with the Si-induced layer-disordering process. For QWH1 the p-n junction and injection is not displaced (as for QWH2) from the QW active region during Si-induced layer disordering (850 °C annealing). A fabrication process is presented in which quantum well laser diodes are built with active regions as narrow in width as 0.6 μm, cw room-temperature laser threshold currents as low as 3 mA, and pulsed current thresholds as low as 1.5 mA.