Structure and composition of interfaces between Ga1−xAlxAs and GaAs layers grown by liquid phase epitaxy (LPE)

Abstract

The structural perfection and composition of interfaces between LPE grown Ga1−xAlxAs and GaAs layers have been analyzed for a large variety of crystal growth conditions. A combination of scanning transmission electron microscopy (STEM) and cathodoluminescence (CL) analysis in the scanning and spectral analysis model has shown the existence of several interfacial features. A compositional grading of the interface was found for LPE interfaces formed by isothermal growth from a saturated melt in the temperature range 750 °–850 °C. The Al concentration in the interface transition region shows variations on a scale of 10–50 μm in the plane of the interface. Its origin is attributed to the fast Al redistribution during the substrate dissolution period which initiates the growth of the LPE layer. Other interfacial features observed correspond to: (a) deep levels associated with the Ge doped Ga1−xAlxAs layers, and (b) meniscus lines which correspond to variations in the Al concentration and impurity segregation producing recombination centers. The role of these interfacial features on the electronic properties of devices should be important for devices which require good carrier confinement and uniform injection.