Normally OFF Hydrogen-Terminated Diamond Field-Effect Transistor With Ti/TiOx Gate Materials

A normally OFF hydrogen-terminated diamond (H-terminated diamond) field-effect transistor (FET) has been successfully achieved with Ti/TiOx gate materials. A 5-nm Ti film was deposited on H-terminated diamond by electron beam evaporation technique and then it was thermally oxidized in air at 120 degrees C for 10 h to form Ti/TiOx, which was confirmed by X-ray photoelectron spectroscopy. The threshold voltage of H-terminated diamond FET is -0.14 V at VDS of -8 V, indicating a normally OFF operation. The normally OFF property could be attributed to the difference of work difference between Ti and H-terminated diamond, which may deplete the hole carriers in H-terminated diamond 2-D hole gas (2DHG) conduction channel. The maximum mobility of H-terminated diamond FET is 313 cm(2)/Vs at VGS of -0.2 V. And, the fixed negative charge density is 3.37 x 10(11) cm(-2). The results demonstrate that Ti/TiOx H-terminated diamond FET is a good solution to fabricate normally OFF device with a simple fabrication process, undamaged 2DHG channel, and uncontaminated interface between Ti and TiOx gatematerials, which may promote the development of normally OFF H-terminated diamond FET.