Deep centers and persistent photocapacitance in AlGaN/GaN high electron mobility transistor structures grown on Si substrates

Deep trap spectra in AlGaN/GaN high electron mobility transistor structures grown on Si by metalorganic chemical vapor deposition show four major electron traps (E-c-0.15, 0.29, 0.40 and 0.76 eV) in the AlGaN barrier/interface region and three (E-c-0.18, 0.27 and 0.45 eV) in the undoped GaN buffer region. The presence of a high density of deep acceptor traps was observed in the AlGaN barrier region, as determined by hysteresis in low temperature capacitance-voltage (C-V) characteristics. The spectral dependence of persistent photocapacitance shifts showed two optical thresholds of 1.5V and 3.1 eV, with the second being specific to structures grown on Si substrates. Comparison of results obtained on transistors and on large-area Schottky diodes prepared on heterostructures from which transistors are fabricated show that measurements on test large-area diodes are representative of the main characteristics important for transistor performance. (C) 2013 American Vacuum Society. [http://dx.doi.org/10.1116/1.4773057]