Growth of thick liquid-phase epitaxial GaAs : Si layers and their characterization

Abstract

In this study we compare some of the characteristic properties of liquid-phase epitaxial (LPE) layers of heavily Si-doped GaAs with those of melt-grown GaAs : Si. LPE layers are grown isothermally at 750, 840, and 910 °C. All the layers are p type and have room-temperature carrier concentrations between 4.2×1017 and 4.8×1018 cm−3. Low-temperature photoluminescence measurements of the layers show a single broad band peaked near 1.32 eV, the peak shifting slightly to lower energy after annealing at 1100 °C. Infrared absorption measurements at ∼80 °K of electron-irradiated layers showed SiGa, SiAs, and SiGa-SiAs localized vibrational modes. The integrated absorptions indicate that the Si site distribution is not compatible with p-type conduction and a new acceptor defect is required. Transmission electron microscopy indicates that the layers have very few vacancy-type prismatic dislocation loops and are essentially free of stacking faults. It is concluded that the LPE layers are basically different than melt-grown GaAs : Si in that different acceptor species, other than SiAs, are present in the two materials and the characteristics of these different acceptors are discussed.