Science and Technology of Super-High Dielectric Constant AlOx/TiOy Nanolaminates on Diamond for MOS Capacitors and MOSFETs

Abstract A super-high dielectric constant AlOx/TiOy nanolaminate film is grown on hydrogenated diamond (H-diamond) to enable superior metal-oxide-semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs). In order to suppress leakage current, a nanometer thick AlOx film is inserted at the AlOx/TiOy nanolaminate/H-diamond interface. The maximum values for the capacitance density and dielectric constant related to the summation of individual AlOx and nanolaminate are 1.06 μF/cm2 and 68.7, respectively. Capacitance density and dielectric constant for the AlOx/TiOy nanolaminate are as high as 5.22 μF/cm2 and 308, respectively. Electrical properties of four H-diamond MOSFETs with gate lengths increasing from 2.4 μm to 10.1 μm were investigated. All of them showed p-type behavior and distinct pinch-off characteristics with drain current maxima of −47.4, −43.3, −26.6, and −24.6 mA/mm, respectively. On/off ratios and threshold voltages for the MOSFETs are higher than 104 and lower than 0.55 ±0.10 V, respectively. The low threshold voltages indicate that the AlOx/TiOy nanolaminate gate-based MOSFETs can switch between ON and OFF stages at low gate voltages. Effective mobilities of the H-diamond channel layers for all the MOSFETs raised firstly and dropped subsequently with increasing voltages, which can be explained by the effect of mobility limiting factors.