Scalable normally-off MIS-HEMT using fluorine implantation below the channel

Abstract

A new normally-off Metal-Insulator-Semiconductor High-Electron-Mobility-Transistor (MIS-HEMT) is proposed. The design is based on the implantation of fluorine ions in the GaN layer below the gate electrode under the AlGaN/GaN interface. Sensitivity analyses are carried out, showing the effects of the fluorine concentration and the thickness of the insulator on the threshold voltage. The limitations and scalability of this technique are pointed out.

DC Gate Leakage Current Model Accounting for Trapping Effects in AlGaN/GaN HEMTs

“…The long channel device under study is a normally-on HEMT on silicon (from a normally-off AlGaN/GaN HEMT using fluorine implantation below the channel [14]), based on the AlGaN/GaN system, 1000 µm wide, with the technological processing carried out at LAAS.…”

“…Numerical simulations have been performed with a Sentaurus Device (from Synopsys) [20]. The transistor DC response, at room temperature, is analyzed solving the Poisson and drift-diffusion equations, together with the heat equation as in [21], polarization charges [22], and the rest of physical parameters from [14]. A gate Schottky diode (i.e., thermionic emission, TE) with Poole-Frenkel (PF) is considered for all operating regimes [23].…”

“…In order to set the threshold voltage, no fitting for the polarization charge is needed (opposite to [14]) when traps under the gate are determined [19], as they (in volume) can modify the Fermi level position in the energy band diagram, or (when superficial) produce a straight-on threshold voltage displacement [24].…”

Numerical Simulation for DC Schottky Gate Leakage Current in AlGaN/GaN HEMTs

“…In this work, the study is focused on a normally-on HEMT on silicon [8], based on the AlGaN/GaN system, 1000 µm wide, with the technological processing carried out at LAAS. Source-to-gate and gate-to-source distances are, respectively, 2 and 5 µm, with a Schottky gate 2 µm long.…”

Normally-off AlGaN/GaN high-electron-mobility transistor on Si(111) by recessed gate and fluorine plasma treatment

“…To realize normally-off operations with AlGaN=GaN HEMT, several structures have been proposed such as the thin AlGaN or recessed gate structure, [10][11][12][13][14] p-GaN or p-AlGaN cap layer, [15][16][17][18] and plasma treatment with high electronegativity ions. [19][20][21][22] However, the reduction of drain current at the same drive voltage is significant compared with untreated normally-on HEMT. In the present study, we investigate the drain current reduction in different depths of recess gate, as well as the relationship between recessed depth and threshold voltage shift.…”