In order to search a gate dielectric with high permittivity on hydrogenated-diamond (H-diamond), LaAlO3 films with thin Al2O3 buffer layers are fabricated on the H-diamond epilayers by sputtering-deposition (SD) and atomic layer deposition (ALD) techniques, respectively. Interfacial band configuration and electrical properties of the SD-LaAlO3/ALD-Al2O3/H-diamond metal- oxide-semiconductor field effect transistors (MOSFETs) with gate lengths of 10, 20, and 30 lm have been investigated. The valence and conduction band offsets of the SD-LaAlO3/ALD-Al2O3 structure are measured by X-ray photoelectron spectroscopy to be 1.160.2 and 1.660.2 eV, respectively. The valence band discontinuity between H-diamond and LaAlO3 is evaluated to be 4.060.2 eV, showing that the MOS structure acts as the gate which controls a hole carrier density. The leakage current density of the SD-LaAlO3/ALD-Al2O3/H-diamond MOS diode is smaller than 10?8Acm?2 at gate bias from ?4 to 2 V. The capacitance-voltage curve in the depletion mode shows sharp dependence, small flat band voltage, and small hysteresis shift, which implies low positive and trapped charge densities. The MOSFETs show p-type channel and complete normally off characteristics with threshold voltages changing from ?3.660.1 to ?5.060.1V dependent on the gate length. The drain current maximum and the extrinsic transconductance of the MOSFET with gate length of 10 lm are ?7.5mAmm?1 and 2.360.1mSmm?1, respectively. The enhancement mode SD-LaAlO3/ALD-Al2O3/H-diamond MOSFET is concluded to be suitable for the applications of high power and high frequency electrical devices.
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