Deep-Level Transient Spectroscopy of Defects in AlGaAsSb/GaAs p–i–n Heterostructures

The study investigates high-voltage gradual p⁰–i–n⁰ junctions in solid solutions of Al_xGa_1 – xAs_1 – ySb_y with y up to 15%, which are capable of absorbing radiation with a wavelength of 1064 nm, grown on GaAs substrates by liquid-phase epitaxy through self-doping with background impurities. The composition of the liquid phase and the temperature range of growth are selected so that the aluminum-compound content x decreased steadily from the specified values of about 34% to a few percent at the surface of the epitaxial layer, while the antimony-compound content y increased. In this case, the band-gap width gradually decreased from the substrate to the surface of the lightly doped layer, reaching the desired value of ~1.16 eV. By measuring the capacity–voltage characteristics and deep level transient spectroscopy in them, configurationally bistable DX centers associated with donor impurities Si and Se/Te are identified. The investigated heterophase epitaxial layers reveal the absence of deep energy levels associated with dislocations. The effective lifetime of minority charge carriers in the base layers of the Al_xGa_1 – xAs_1 – ySb_y/GaAs diode is determined using reverse recovery of the diode. Assuming that the minority-carrier lifetime is mainly determined by the capture of holes by the acceptor-like deep level DX ^– of Si in the n⁰ layer of the material, the hole capture cross section on the DX ^– level is estimated. The capture cross section is found to be 6 × 10^–15 cm².