Defect related optical and electrical properties of mbe grown cubic GaN epilayers

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Abstract
The optical and electrical properties of cubic GaN (c-GaN) epilayers are characterized by low temperature photoluminescence (PL), spatially resolved cathodoluminescence (CL) and temperature dependent Hall-effect measurements. Cubic GaN layers have been deposited by plasma assisted molecular beam epitaxy on semi-insulating (001) GaAs-substrates. The growth conditions are controlled by in situ reflection high energy electron diffraction (RHEED) measurements. The nature of the defects observed by the three measurement techniques is discussed in view of intrinsic defects proposed by theoretical calculations and in view of an omnipresent residual carbon contamination. A simple compensation model can explain the conversion of conductivity from p-type c-GaN to n-type c-GaN epilayers by increasing the Ga to N ratio during growth. The relevance of a deep transition at 2.4 eV observed by CL at 300 K is excluded for the performance of optoelectronic devices like laser diodes.