Dislocations introduced in n-GaN at room temperature cause conductivity inversion

Dislocations were introduced by scratching at room temperature of the surface of n-GaN films grown by Metalorganic Chemical Vapor Deposition (MOCVD) on basal plane sapphire. The dislocations were observed to propagate from the scratch along the<11–20> directions along several slip systems and form a region with high dislocation density extending by 30–40 µm on each side of the scratch. The regions with enhanced dislocation density were characterized by a strong decrease of intensity of bandedge cathodoluminescence (CL) band at 368 nm, an emergence of the dislocation-related band at 400 nm wavelength, and a strong increase in intensity of the yellow CL band related to defects. Capacitance-voltage and current-voltage measurements in the dark and under illumination performed as a function of temperature indicates that the region with enhanced dislocation density is converted to p-type. Measurements of current versus temperature, admittance spectra, and Deep Level Transient Spectroscopy (DLTS) allowed for the first time to determine the energy position of dislocation-related acceptors level near Ev+ 0.35 eV and to estimate their concentration.