Electrical characteristics of low-Mg-doped p-AlGaN and p-InGaN Schottky contacts

Electrical characteristics of low-Mg-doped p-Al0.02-0.07Ga0.98-0.93N and p-In0.02Ga0.98N Schottky contacts were investigated. A memory effect was revealed in the current-voltage (I-V) characteristics, which is found also in p-GaN contacts and may be due to charge and discharge of holes to acceptor-type interfacial defects. High-temperature isothermal transient spectroscopy revealed that the defect densities in the Al0.02Ga0.98N and In0.02Ga0.98N samples were nearly half that in the GaN samples. A large reverse current with a memory effect was observed in the In0.02Ga0.98N contacts. It was suggested that current can flow via relatively shallow acceptor-type interfacial defects. For the AlxGa1-xN with x = 0.04 and 0.07, I-V characteristics became leaky. The Schottky barrier heights estimated from the photoresponse experiment were higher than the values estimated from the bandgap by 0.19, 0.21, 0.20, and 0.21 eV for Al0.02Ga0.98N, Al0.04Ga0.96N, Al0.07Ga0.93N, and In0.02Ga0.98N samples, respectively. A probable explanation for such discrepancies may be due to the total charge amount of the interfacial states, which varied the electric field and the barrier lowering. It was found that even though the Al or In content was only as small as 2%, the electrical characteristics of the contacts changed significantly. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim