In this paper, we present an electrical study of InN thin films elaborated by nitridation of InP (100) substrates. The samples have been obtained using a glow discharge source (GDS) in ultra-high vacuum. The gold (Au) Schottky contact was deposited on the top of the surface. The electrical characteristics of Au/InN/n-InP structure have been investigated using current-voltage and capacitance-voltage methods. We show from the current-voltage characterization at room temperature that the main conduction mechanism is thermionic emission current. A value of 1.57 for the ideality factor of the diode is extracted using analytical methods. Furthermore, the barrier height of the device is evaluated to 0.64 eV. This value is substantially larger than previously reported in the literature. The low saturation current and series resistance (Rs) of 12.3 A and 38 Ω, respectively, indicate the presence of the InN layer. From the capacitance-voltage technique under reverse bias, the built-in potential and the ionized donor concentration are 0.83 V and 1.16 10 17 cm -3 , respectively. A frequency dependent capacitance is measured and attributed to the presence of interface states. Based on the high-low frequency method, we determined the average density of interface states (Nss) with a value of 5.6 10 11 eV -1 cm -2 . These findings reveal good passivation of the InP surface with the use of a thin InN film.
In this paper, an AIGaN/GaN metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT) device is realized. The device shows normal ON characteristics with a maximum current of 570 mA/mm at a gate-to-source voltage of 3 V, an on-state resistance of 7.3 Ω·mm and breakdown voltage of 500 V. The device has been modeled using numerical simulations to reproduce output and transfer characteristics. We identify, via experimental results and TCAD simulations, the main physical mechanisms responsible for the premature breakdown. The contribution of the AlN/Silicon substrate interface to the premature off-state breakdown is pointed out. Vertical leakage in lateral GaN devices significantly contributes to the off-state breakdown at high blocking voltages. The parasitic current path leads to premature breakdown before the appearance of avalanche or dielectric breakdown. A comparative study between a MOS-HEMT GaN on a silicon substrate with and without a SiNx interlayer at the AlN/Silicon substrate interface is presented here. We show that it is possible to increase the breakdown voltages of the fabricated transistors on a silicon substrate using SiNx interlayer.
A cost-effective fabrication process is developed to improve the power performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs). This process uses nitrogen ion (N + ) implantation to form multiple parallel NanoRibbons on AlGaN/GaN heterostructures, with thin buffer layer (AlGaN/GaN NR-HEMTs). SRIM simulations of the N + implantation combined with measured current-field characteristics reveal a good electrical isolation beneath the 2-dimensional electron gas (2DEG), resulting in substantial increase of the breakdown field of the NR-HEMTs, when compared to conventional AlGaN/GaN HEMTs. The fabricated AlGaN/GaN NR-HEMTs performed (i) an ON/OFF current ratio more than two orders of magnitude larger and (ii) a buffer leakage current more than one order of magnitude weaker than that of the conventional AlGaN/GaN HEMTs. The on-resistance, RON, and series resistance, RS, of AlGaN/GaN NR-HEMTs are both reduced by one order of magnitude, when compared to those of the conventional AlGaN/GaN HEMTs. These have boosted the drive current density by up to 435%. Furthermore, we have found that the architecture of the AlGaN/GaN NR-HEMTs reduces the destructive impact of electron traps in the device. An optimized AlGaN/GaN NR-HEMT exhibited a better electrostatic integrity, a subthreshold slope of ∼210 mV/dec instead of 730 mV/dec for a conventional GaN HEMT. A higher linearity in the transconductance, gm, of NR-HEMTs is observed, twice of that of a conventional GaN HEMT. These results demonstrate the great interest of developed process technology, of NR-HEMTs, for high-power switching applications.
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