Schottky barrier transport in InSb/AlInSb quantum well field effect transistor structures

Gate leakage currents in high performance InSb/AlInSb quantum well field effect transistors are presented. Thermionic emission theory for Schottky contacts, including the Schottky effect (image force lowering), is successfully used to explain the form of the gate leakage current as a function of gate voltage (I(V-g)) at room temperature. A value for the unlowered Schottky barrier height is extracted from this analysis (similar to 210 meV). The measurement of barrier height is seen to be in good agreement with the assertion that the Al0.15In0.85Sb material system exhibits mid-bandgap pinning at the metal-semiconductor interface. Gate current as a function of temperature is also used to extract barrier heights, using Arrhenius style plots, and they are shown to be consistent with thermionic emission over an image force lowered barrier. Low temperature I(V-g) data are also presented whereby the gate current is seen to increase below similar to 30 K. This effect is unexpected and is attributed to possible movement of the pinning level at the metal-semiconductor interface.