P- and N-Type Doping of Mbe Grown Cubic GaN/GaAs Epilayers

Abstract

AbstractP-type doping with Mg and n-type doping with Si of cubic GaN (c-GaN) epilayers is reported. Cubic GaN films are grown by if-plasma assisted MBE on semi-insulating GaAs (001) substrates at a substrate temperature of 720°C. Elemental Mg and Si are evaporated from thermal effusions cells. Secondary ion mass spectroscopy (SIMS), low temperature photoluminescence (PL) and temperature dependent Hall-effect measurements are used to study the incorporation, optical and electrical properties. A Mg related shallow donor-acceptor transiton at 3.04 eV with an acceptor activation energy of EA= 0.230 eV is observed by low temperature PL. At Mg concentrations above 1018 cm-3 the dominance of a broad blue band indicates that also in c-GaN Mg is incorporated at different lattice sites or forms complexes. Si-doped c-GaN epilayers are n-type with electron concentrations up to 5*1019 cm-3. The incorporation of Si follows exactly the vapor pressure curve of Si, indicating a sticking coefficient of I for Si in c-GaN. With increasing Si-concentration the intensity of the near-band luminescence continuously increases and broadens.