Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy.

In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77 K-350 K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (µ-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E1 = 0.65 eV, σ1 = 8.2 x 10-16 cm² and E2 = 0.58 eV, σ2 = 2.6 x 10-15 cm² whereas for the two low-temperature majority traps they were equal to E3 = 0.18 eV, 3 = 9.7 x 10-18 cm² and E4 = 0.13 eV, =σ4 = 9.2 x 10-18 cm² . The possible origin of the traps is discussed and the results are compared with data reported elsewhere. [ABSTRACT FROM AUTHOR]