Surface and interfacial properties of Ga0.47In0.53As–Al2O3 MIS structures

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Abstract
Field-effect-controlled electrical and galvanomagnetic measurements have been made on transistorlike five-terminal metal insulator semiconductor (MIS) structures using n-type 0.25 μm thick Ga0.47In0.53As epitaxial layers grown on semi-insulating InP substrates. These layers have an electron density n=3.5×1016 cm−3 and a mobility μn=7.5×103 cm2/V-s; 0.13 μm thick Al2O3 dielectric layers, grown by a rf plasma-assisted low temperature chemical-vapor deposition (CVD) process were employed as gate insulators under 0.01 cm2 vacuum-deposited aluminum gates. Hall effect and resistivity measurements were made on such structures and the experimentally observed gate voltage dependent change in resistivity and Hall coefficient of the conducting channel under the gate have been related to the corresponding change in the depletion depth of the surface space charge region. The data were used to derive the density of the surface states and their position within the fundamental band gap of Ga0.47In0.53As. We find that the surface Fermi level E*F of virgin MIS structures is pinned ∼0.2 eV below the conduction band minimum (0.55 eV above the valence band maximum) of Ga0.47In0.53As, in agreement with the experimentally measured and theoretically calculated barrier height of metal Ga0.47In0.53As diodes. Annealing at 120 °C for 16 h reduces the density of interface states by more than a factor of 2 and eliminates Fermi level pinning allowing the surface potential to be displaced over a substantial fraction of the fundamental band gap, in agreement with data derived from C–V measurements made on MIS structures with different types of dielectric layers using different annealing procedures.

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