In situ flashes of gallium technique for oxide-free epiready GaSb (100) surface

Abstract

The authors report a novel in situ technique for desorption of native oxides from GaSb (100) substrates. In the proposed approach, flashes of atomic gallium (FLAG) are irradiated onto a heated substrate to convert the nonvolatile Ga2O3 to volatile Ga2O. The conventional thermal oxide desorption (TOD) technique was compared with the proposed FLAG technique. Reflection high energy electron diffraction was used to monitor the oxide desorption. Oxide desorption by the FLAG technique was observed at 470 °C, which is ∼80 °C lower than the TOD technique (550 °C). Atomic force microscopy of the GaSb buffer grown using the FLAG technique reveals an atomically smooth surface. Unipolar barrier midwave infrared detectors based on InAs/GaSb type II superlattices were grown using the two approaches. The dark current from a representative FLAG device measured at T = 77 K and Vb = −0.1 V was 5.28 × 10−6 A/cm2 compared with a reference TOD device which had a dark current of 8.96 × 10−4 A/cm2 measured under identical conditions. The quantum efficiency at λ = 4.5 μm, T = 77 K, Vb = 0 V was measured to be 51% for the FLAG detector and 24% for the reference TOD detector. The FLAG technique was tested on several substrates of varying thickness of the native oxide. Also, the number of Ga-flashes was optimized to get a good starting epiready surface. The authors believe that they have established a promising technique for the in situ preparation of an epiready growth surface without the need for any ex situ treatment.