Investigations on electrical characteristics and reliability properties of MOS capacitors using HfAlOx on n-GaAs substrates

Radio frequency sputtering system is employed to fabricate metal oxide semiconductor (MOS) capacitors using an ultra-thin layer of HfAlOx dielectric deposited on n-GaAs substrates with and without a Si interface control layer incorporated in between the dielectric and the semiconductor. Measurements are performed to obtain capacitance voltage (C–V) and current voltage (I–V) characteristics for GaAs/Si/HfAlOx and GaAs/HfAlOx capacitors under different constant voltage and constant current stress conditions. The variation of different electrical parameters such as change in interface trap density, hysteresis voltage with various values of constant voltage stress and the dependence of flat band voltage, fractional change in gate leakage current density, etc. with stress time are extracted from the C–V and I–V data for capacitors with and without a Si interlayer. Further the trap charge density and the movement of trap centroid are investigated for various injected influences. The dielectric breakdown and reliability properties of the dielectric films are studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, tbd ⩾ 1350 s) is observed for HfAlOx gate dielectric with a silicon inter-layer under the high constant voltage stress at 8 V. Compared to capacitors without a Si interlayer, MOS capacitors with a Si interlayer exhibit improved electrical and breakdown characteristics, and excellent interface and reliability properties.

► GaAs MOS capacitors were fabricated using RF sputtered HfAlOx gate dielectrics.
► Si ICL is introduced to improve the interfacial properties.
► The electrical parameters under different stressed conditions are extracted and compared.
► The trap charge density and centroid are investigated under CCS.
► A high tbd is reported for HfAlOx gate dielectric with a silicon inter-layer.