Bulk noise processes and their correlation to structural imperfections in magnesium-doped p-type GaN grown on sapphire

We investigate the noise properties of p-type Mg-doped GaN using low frequency noise spectroscopy. The epitaxial GaN:Mg films were grown on a sapphire substrate by metalorganic chemical vapor deposition in different laboratories. Generation-recombination (g-r) noise and one-over-f (1/f) noise are observed for temperatures above 250 K. The magnitude of the 1/f noise exceeds the g-r noise magnitude for frequencies less than 30 Hz, and the 1/f noise level is characterized by high values of the Hooge parameter, alpha approximate to 1-150, indicating a high level of structural imperfection. In addition, the integrated noise power spectral density divided by the voltage squared in the frequency range of 1 to 30 Hz, correlates strongly with the structural imperfection of the sample as measured from the asymmetric rocking curve (omega scan) full width at half maximum. The generation-recombination noise is related to a high concentration trap level with an activation energy of 120 +/- 25 meV and a repulsive barrier that is possibly associated with the Mg dopant. (C) 2000 American Institute of Physics. [S0021- 8979(00)05711-X].