Optimization of GaMnAs growth in low temperature molecular beam epitaxy

We present a detailed growth optimization procedure and experimental results for the growth of GaMnAs magnetic semiconductors in low-temperature molecular beam epitaxy. They were explored by using in-situ monitoring of the surface reconstruction patterns, double crystal/high-resolution x-ray diffraction, conductivity measurement, and superconducting quantum interference device measurements. The results showed strong correlations among the measurements. The room temperature conductivity measurement, in particular, was found to be a useful tool in forecasting the ferromagnetic transition temperature of the films. High quality GaMnAs films could contain Mn up to ≈5% without MnAs segregation at substrate temperatures of 215–275°C. The highest transition temperature of 80 K, however, was measured from the sample with 3.7% Mn grown at the substrate temperature of 250°C and As4 pressure of 1.4×10−6 torr for a growth rate of 0.25 μm/hr.