A STUDY OF THE TRANSITION FROM HIGH TO LOW-RESISTIVITY IN AS-GROWN GAAS MBE MATERIAL

This work discusses the transition from high resistivity as-grown GaAs layers to thermally metastable low resistivity as-grown layers by mol ecular beam epitaxy. This transition occurs at about 430 degrees C and coincides with a reflective high energy electron diffraction reconstr uction change from a 2 x 1 to 2 x 4 pattern for an As-4/Ga beam equiva lent pressure ratio of 20. For growth temperatures in the range 350 to 430 degrees C, room temperature Hall-effect measurements have shown r esistivities of >10(7) ohm-cm and photoluminescence has shown new peak s at 0.747 eV and a band from 0.708 to 0.716 eV at 4.2K, in unannealed material.