Deep Electronic Levels of Al_xGa_(1-x)N with a Wide Range of Al Composition Grown by Metal-Organic Vapor Phase Epitaxy

摘要

Deep electronic levels of Al_(x)Ga_(1-x)N (0.25 < x < 0.60) were investigated by deep level transient spectroscopy (DLTS) and photocapacitance methods. Si-doped AIGaN layers were grown on an AIN/sapphire template by metal-organic vapor phase epitaxy. DLTS analysis using a sampling time window of up to 100s showed two dominant deep levels with activation energies (ΔE) higher than 1.0eV in Al_(x)Ga_(1-x)N with x = 0.25 and 0.37. The densities of those levels were higher than 1 x 10~(16)cm~(-3). For the Al_(0.60)Ga_(0.40)N sample, the deeper levels (ΔE > 1.5eV) were detected by photocapacitance measurement. It was found that the energy position of the dominant deep level closely followed the Fermi level stabilization energy reported by Walukiewicz et al. [J. Cryst. Growth 269 (2004) 119], indicating that the origin of the dominant deep level in AIGaN is related to a defect complex including anti-site defects and divacancies.