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Multi-quantum-well GaN/InGaN heterojunction diodes prepared by metalorganic chemical vapor deposition on sapphire showed effects of strong tunneling in their I–V characteristics. The space charge region was shown to be located in the GaN/InGaN superlattice (SL). The injection of moderately high forward currents through the structure for several hours enhanced the overall tunneling through the structure and facilitated faster tunneling between the layers in the GaN/InGaN SL. These results may have relevance to the aging characteristics of light-emitting diodes under bias. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pt contacted AlGaN/GaN high electron mobility transistors with Sc2O3 gate dielectrics show reversible changes in drain–source current upon exposure to H2-containing ambients, even at room temperature. The changes in current (as high as 3 mA for relatively low gate voltage and drain–source voltage) are approximately an order of magnitude larger than for Pt/GaN Schottky diodes and a factor of 5 larger than Sc2O3/AlGaN/GaN metal–oxide–semiconductor (MOS) diodes exposed under the same conditions. This shows the advantage of using a transistor structure in which the gain produces larger current changes upon exposure to hydrogen-containing ambients. The increase in current is the result of a decrease in effective barrier height of the MOS gate of 30–50 mV at 25 °C for 10% H2/90% N2 ambients relative to pure N2 and is due to catalytic dissociation of the H2 on the Pt contact, followed by diffusion to the Sc2O3/AlGaN interface. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The capacitance-voltage (C-V) characteristics of Sc[sub 2]O[sub 3]/p-GaN gate-controlled diodes show unusual hook shapes due to the charging of surface states. From the drain-voltage dependence of the C-V curves, the total surface state density was estimated to be ∼ 8.2 × 10[sup 12] cm[sup -2] for diodes undergoing an implant activation anneal at 950°C. The accumulation capacitance showed a significant dependence on measurement frequency and is suggested to result from the presence of an interfacial dielectric between the Sc[sub 2]O[sub 3] and GaN. The Si-implanted n [sup +] regions in the gated diode structure are effective in providing a source of inversion charge. [ABSTRACT FROM AUTHOR]

GaN/SiC and Al0.25Ga0.75 N/SiC heterojunction diodes were fabricated using Al/Ti for p-ohmic contact to the SiC and Ti/Al/Pt/Au for n-ohmic contact to the GaN and AlGaN. Annealing at 850 °C for 20 s (GaN) or 120 s (AlGaN) was required for achieving specific contact resistances in the 10−6 Ω cm2 range. The reverse breakdown voltage showed a negative temperature coefficient in both types of sample, with value ∼5.5±2.5×10−3 V/K. The I–V characteristics of both heterojunctions show evidence of tunneling via defect states. [Copyright &y& Elsevier]