We present an instability investigation of In0.7Ga0.3As quantum-well (QW) metal-oxide-semiconductor field-effect-transistors (MOSFETs) on InP substrate with Al2O3 and Al2O3/HfO2 gate stacks. The device with bi-layer Al2O3/HfO2 gate stack exhibits larger shift in threshold-voltage (DVT) under a constantvoltage- stress condition (CVS), than one with single Al2O3 gate stack. At cryogenic temperature, the device with bi-layer Al2O3/HfO2 gate stack also induces worse hysteresis behavior than one with single Al2O3 gate stack. These are mainly attributed to more traps inside the HfO2 material, yielding a charge build-up inside the HfO2 gate dielectric. This strongly calls for a follow-up process to minimize those traps within the high-k dielectric layer and eventually to improve the reliability of InGaAs MOSFETs with HfO2-based high-k gate dielectric. (C) 2016 Published by Elsevier Ltd.