A Study of Recombination Centers Related to As-Sb Nanoclusters in Low-Temperature Grown Gallium Arsenide

Electronic traps in 'low-temperature' GaAs (LT-GaAs) grown at 150 deg. C were studied. The As-Sb clusters appearing in this material after annealing were located in a plane that contained a single Sb monolayer formed during growth. The diameter of the clusters was as large as 20 nm. For the purpose of measurement, Au-n-GaAs Schottky barriers were used, in which, for certain bias voltages, the space charge region enclosed the narrow LT-GaAs layer containing the plane of clusters. The bias-voltage dependence of the structure capacitance indicates that the majority of the electrons in this layer are captured by traps, whose energy level lies ∼0.5 eV below the bottom of the conduction band. The energy density of states at this energy is 1014 cm-2 eV-1, which sharply decreases towards the midgap. The existence of traps with activation energies of ∼0.5 eV for the thermal emission of electrons is confirmed by deep-level transient spectroscopy. The magnitude of the electron-capture cross section determined by this method is in the range 5 x 10-14-1 x 10-12 cm2. It is assumed that traps of this type are related to large As-Sb clusters