Growth of low resistivity p-type GaN by metal organic chemical vapour deposition

Mg-doped GaN epitaxial layers were grown on (0001) sapphire by metal organic chemical vapour deposition and were characterised by room-temperature and variable-temperature Hall-effect measurements. The authors report an in-situ Mg acceptor activation procedure which occurs in a N₂ ambient during the post-growth cool-down cycle. GaN:Mg films with a wide range of free-hole concentrations and electrical resistivities have been grown by varying the Mg precursor molar flow rate, the growth pressure, and the growth temperature. The highest 300 K free hole concentrations achieved were p≃2.2×10 ¹⁸ cm^-3 with mobilities μ_p≃2.2 cm²/Vs