Effect of Sputter Deposition Atmosphere of AlN on the Electrical Properties of Hydrogen‐Terminated Diamond Field Effect Transistor with AlN/Al2O3 Stack Gate

Abstract

The electrical properties of hydrogen‐terminated diamond (H‐diamond) metal–insulator–‐semiconductor field‐effect transistor (MISFET) are improved remarkably using AlN/Al2O3 stack gate. Atomic‐layer‐deposited Al2O3 (ALD‐Al2O3) is formed on H‐diamond to protect the hole conductive layer at the surface, followed by the sputter‐deposited AlN (SD‐AlN) under mixed Ar+N2 atmosphere. The insulating property of SD‐AlN under mixed Ar+N2 atmosphere is highly improved compared with that of SD‐AlN under pure Ar atmosphere. In addition, the positive charges in the SD‐AlN are reduced upon the mixed Ar+N2 atmosphere sputter condition. These results could be attributed to the improved electrical properties of H‐diamond MISFET and MIS diode with SD‐AlN/ALD‐Al2O3 stack gate. The MIS diode provides a leakage current density as low as ≈1.25 × 10−6 A cm−2 at gate voltage bias in the range of −20 and +4 V. The capacitance–voltage curve shows an almost no flat‐band voltage shift, and the value of effective dielectric constant of SD‐AlN approaches close to that of bulk AlN. The MISFET shows normally on depletion mode transfer characteristic. The drain–source current maximum, threshold voltage, and maximum extrinsic conductance of the MISFET with 4 μm gate length are around −58.4 mA mm−1, +1.2 V, and 7.49 mS mm−1.