Characteristics of p-type GaN formed by two different types of Mg diffusion

Two different types of magnesium (Mg) diffusion onto intentionally undoped n-type GaN, resulting in p-type GaN formation, have been employed in this work. Secondary-ion mass spectroscopy (SIMS) measurements reveal a uniform Mg concentration for both methods of diffusion up to a depth of 1.5 mu m in GaN. Hall measurement data indicate that all the diffused and annealed samples consistently show p-type conductivity with hole concentrations in the range of 5 similar to 7 x 10(16)/cm(3) and with mobilities < 50 cm(2)/V.s. The measured dark current of the samples almost exponentially increases with the reciprocal temperature with an activation energy of 144 meV or 168 meV in the temperature range from 170 K to 250 K. The photoluminescence (PL) spectra of Mg diffused GaN show a broad violet emission at around 3.15 eV. This broad peak may be attributed to Mg acceptors. In the photocurrent (PC) measurements on the Mg/Au film deposited on n-type GaN, an additional broad peak was observed at around 1.2 eV, and this peak may be related to the yellow luminescence.