Fabrication of dry-etched cavity GaAs/AlGaAs multiquantum-well lasers with high spatial uniformity

In order to obtain dry-etched lasers with high spatial uniformity, the relation between the etching profile and the laser structure is investigated in detail for two types of GaAs/AlGaAs multiquantum-well lasers, with and without selective Zn diffusion, with reactive-ion-beam-etched facets. It is found that a laser structure with an abrupt step on the surface locally roughens the facets during etching through the generation of etching residues on the etched bottom. Such an abrupt step on a wafer can be typically introduced by the conventional selective Zn-diffusion process including surface chemical treatment. The etched lasers fabricated with the selective Zn-diffusion process show a wide distribution in the threshold current. In contrast, the lasers without the selective diffusion process realize a narrow distribution in the theshold current.