In this paper, reverse-biased gate leakage current in Al2O3/InAlAs metal-oxide-semiconductor (MOS) structures has been investigated. The current-voltage (I-V) characteristics were measured from 283 to 343 K with a step of 20 K. It is found that Schottky emission is dominant at low reverse bias (<0.4 V). The dynamic dielectric constant of Al2O3 and the Schottky barrier height determined by the linear fitting are 2.19 and 0.70 +/- 0.01 eV, respectively. However, beyond the Schottky emission region, leakage current follows space charge limited (SCL) conduction. Trap-filled limited (TFL) conduction is observed at all the measurement temperatures, whereas Ohm's lawis only observed at 343 K and transition between TFL conduction and Child's lawis only observed at 323 and 343 K. This phenomenon could be ascribed to different transition conditions at different measurement temperatures. Besides, the potential well depth of traps (E-c - E-t) calculated from TFL conduction is 0.40 +/- 0.01 eV. (C) 2016 Elsevier B.V. All rights reserved.