Molecular doping of gallium nitride

Photoconductivity experiments were made on bulk GaN doped with Mg and O and grown using high pressures and high temperature. The bulk GaN: Mg, O was i nsulating, indicating compensation. The photoconductive response to photons above the energy band gap was comparable to that of epitaxially grown GaN: Mg samples. However, the UV-to-visible rejection ratio (solar blindness) w as three orders of magnitude larger in the bulk GaN: Mg, O than for other e pitaxially grown GaN samples. The dramatically improved visible rejection r atio is tentatively attributed to molecular doping by paired donors (O) and acceptors (Mg). Vacuum UV reflectance was performed to verify if MgO criti cal point transitions could be found in the GaN: Mg, O. A reflectance peak at 6.7 eV was found in both MgO and GaN: Mg, O. (C) 1999 American Institute of Physics. [S0003-6951(99)02403-1].