Control of surface states in GaSb/AlxGa1−xAsySb1−y/GaxIn1−xSb/AlxGa1−xAsySb1−y quantum well structures

GaSb-based lasers show advanced capabilities over other material for the far-infrared wavelength range. However, for quantum-well (QW) laser structures of AlxGa1−xAsySb1−y/GaxIn1−xAsySb1−y/AlxGa1−xAsySb1−y grown on GaSb, each component element etches at a different rate, making it difficult to achieve quality surfaces sufficiently free of defects. Thus, in this letter, the effects on the surface quality of GaSb-based laser materials have been studied using phosphoric acid etching, boron trichloride reactive ion etching (RIE), and a postetch sulfur treatment. In addition, the quality of the surface is compared for two barriers of AlAs0.07Sb0.93 and Al0.9Ga0.1As0.07Sb0.93, based on current–voltage measurements as a function of temperature. The best surfaces were produced by RIE and by using as much Ga in the barriers as the device operation allows. A generation center in the Ga0.81In0.19As0.12Sb0.88 was found at 0.14 eV for QW diodes with low surface conduction.