INVESTIGATION OF Si RELATED DEEP ACCEPTOR LEVEL IN AS GROWN GaN BY DLTS

In this study, we have investigated the origin of an acceptor level in as grownGaN thin films grown by MBE on Si substrate. DLTS measurements revealed the presence of anacceptor defect level in the band gap of GaN with activation energy E-a = 0.23 +/- 0.01eV, capture cross section 3.18 x 10(-18) cm(2) and trap concentration 6.0 x 10(14) cm(-3). This defect level may be correlated to the silicon incorporation into GaN due to high substrate temperature during GaN film growth and the same might be responsible for the so called p-type conductivity of GaN layer. The transport of out-diffused Si atoms into GaN is through the voids presents in the grown film. The density of carriers at GaN/Si interface is high as compared to surface of GaN demonstrated by depth profiling of carriers. The presence of Si in GaN is further justified using photoluminescence and Raman spectroscopy measurements.