High resolution Laplace deep level transient spectroscopy studies of electron and hole traps in n-type GaN

Deep Level Transient Spectroscopy (DLTS) and Laplace DLTS (LDLTS) have been applied to MOVPE-grown n-type GaN, grown at 1920 degrees C on c-plane sapphire. DLTS measured up to 600 K initially recorded three peaks due to electron emission. However, when the next rate window was sampled immediately afterwards, the DLTS scan showed a large negative peak which dominated the scan at 410K. The polarity of the feature means that this is due to hole mission. An electron, trap initially present at 400 K in the DLTS spectrum gradually disappeared up to a measurement temperature of 520 K; beyond this the hole trap was observed. It then remained detectable, by DLTS for up to one week, although cooling under bias decreased its intensity severely. LDLTS reveals that this hole trap is not a simple point defect as it has three emission rates. It is discussed in the context of the V-Ga- O-N(X) defect, where different mission rates present could reflect V-Ga complexed with different numbers of O atoms.