An enhanced two-dimensional hole gas (2DHG) C–H diamond with positive surface charge model for advanced normally-off MOSFET devices

Abstract

Though the complementary power field effect transistors (FETs), e.g., metal–oxide–semiconductor-FETs (MOSFETs) based on wide bandgap materials, enable low switching losses and on-resistance, p-channel FETs are not feasible in any wide bandgap material other than diamond. In this paper, we propose the first work to investigate the impact of fixed positive surface charge density on achieving normally-off and controlling threshold voltage operation obtained on p-channel two-dimensional hole gas (2DHG) hydrogen-terminated (C-H) diamond FET using nitrogen doping in the diamond substrate. In general, a p-channel diamond MOSFET demonstrates the normally-on operation, but the normally-off operation is also a critical requirement of the feasible electronic power devices in terms of safety operation. The characteristics of the C–H diamond MOSFET have been analyzed with the two demonstrated charge sheet models using the two-dimensional Silvaco Atlas TCAD. It shows that the fixed-Fermi level in the bulk diamond is 1.7 eV (donor level) from the conduction band minimum. However, the upward band bending has been obtained at Al2O3/SiO2/C-H diamond interface indicating the presence of inversion layer without gate voltage. The fixed negative charge model exhibits a strong inversion layer for normally-on FET operation, while the fixed positive charge model shows a weak inversion for normally-off operation. The maximum current density of a fixed positive interface charge model of the Al2O3/C-H diamond device is − 290 mA/mm, which corresponds to that of expermental result of Al2O3/SiO2/C-H diamond − 305 mA/mm at a gate-source voltage of − 40 V. Also, the threshold voltage Vth is relatively high at Vth = − 3.5 V, i.e., the positive charge model can reproduce the normally-off operation. Moreover, we also demonstrate that the Vth and transconductance gm correspond to those of the experimental work.

Normally-off Hydrogen-Terminated Diamond Field-Effect Transistor with SnOx Dielectric Layer Formed by Thermal Oxidation of Sn

“…Compared with traditional semiconductor materials (e.g., Si, GaN, and SiC), diamond has many outstanding properties, including a large band gap (5.45 eV), high carrier mobilities (electron: 4500 cm 2 V −1 s − 1 , hole: 3800 cm 2 V −1 s −1 ), high thermal conductivity (22 W K −1 cm −1 ), and a high breakdown field (>10 MV cm −1 ) [ 1 ], making it a potential wide band gap semiconductor material for next-generation high-frequency and high-power electronic devices [ 2 , 3 , 4 ]. Devices based on diamond have been studied for a long time, such as metal insulator semiconductor field effect transistors (MISFETs) [ 5 ], microelectromechanical systems [ 6 ], UV photodetectors [ 7 ], Schottky diode [ 8 ], biosensors, and so on.…”

“…The conductivity of H-diamond comes from a surface transfer doping process [ 9 ] and the holes residing in an accumulation layer at the hydrogenated diamond surface [ 10 ]. Additionally, the surface charge density located nearby the interface is around 10 13 cm −2 [ 1 ]. In this case, the H-diamond MISFET device usually shows a depletion mode.…”