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An extensive study is conducted to evaluate breakdown mechanisms in gallium nitride (GaN) high electron mobility transistors (HEMT). A comprehensive physics-based model of a common HEMT provides the base comparison to conduct different material and geometric investigations. The variations are evaluated in a progression toward the optimal configuration: 1) varying the passivation material, 2) replacing...
The AlGaN/GaN high electron mobility transistor using 30-nm ALD La2O3 passivation has been fabricated. Compared with the non-passivation HEMT, the breakdown voltage Vbr of La2O3 passivation HEMT can be improved from 115 V to 134 V. 2-D simulation is adopted to explain the phenomenon. The reason for enhanced Vbr in La2O3 passivation HEMT is due to high permittivity er of La2O3 dielectric with drain...
In this work, we investigated the mechanisms of nitride-based passivation (i.e. SiNx and AlN) and their impact on high-voltage switching of AlGaN/GaN heterojunction power transistors with TCAD simulations. It was found that they play a vital role for nitride-passivated devices to simultaneously achieve low dynamic ON-resistance (Ron) and uncompromised breakdown capability. Simulated 2-D electrostatic...
A novel AlGaN/GaN-based HEMT using gate recess technology is designed and simulated by deploying both Si3N4/SiO2 passivation layers on SiC substrate using Synopsys Tcad tools. The drain current of the proposed device is measured to be 726mA at a threshold voltage of −1.2V from the study of the DC characteristics of the device. The RF characteristics of the GaN/AlGaN HEMT is analyzed by the AC analysis...
GaN-on-Si MOSHEMTs are fabricated with gate-recessed structure. It is found that surface damages introduced by plasma bombardment during recess etch at oxide-semiconductor interface cause instability of threshold voltage of the devices. To eliminate the surface damages, KOH passivation is applied and the effect is studied in this report. Hysteresis is inhibited and the flat-band voltage shift reduces...
A Low-Pressure-Chemical-Vapor-Deposition (LPCVD) bilayer SiNx passivation scheme has been investigated and developed, which effectively suppress the current collapse in AlGaN/GaN HEMTs. Low current slump is very helpful for microwave power amplifier application. Compared to in-situ SiNx passivations by metal-organic-chemical-vapor-deposition (MOCVD) and ex-situ SiNx passivations by plasma-enhanced-chemical-vapor-deposition...
Using TCAD simulation, we studied the stress effect of pseudomorphically grown Al0.25Ga0.75N barrier and passivation nitride with intrinsic stress on the electrical characteristics of AlGaN/GaN HEMT. It is found that barrier stress can reduce the two-dimensional electron gas (2DEG) by as much as 15% and change the current by more than 10%, depending on the deformation potential values. Therefore,...
The changes in dc characteristics of AlGaN/GaN HEMT after ICP-CVD silicon nitride (SiNx) passivation using two different recipes were investigated. Room temperature Raman analysis was performed to determine the stress state of the AlGaN layer after SiNx passivation. The changes in the stress state of the device after passivation was correlated with the shift in threshold voltage and changes in drain...
The role of SiNx passivation using two different deposition techniques, namely Inductively Coupled Plasma Chemical Vapor Deposition (ICPCVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) on gate reverse leakage current of AlGaN/GaN HEMTs was studied. It was observed that devices having PECVD SiNx films exhibit higher leakage than devices with ICPCVD SiNx films. To understand the mechanism...
A physics-based analytical modeling for the gas sensor application of AlGaN/GaN heterostructure Schottky diode has been investigated for high linearity and sensitivity of the device. The heterointerface and surface properties are exploited here. The dependency of 2DEG on the surface charge, which is dependent on the Si3N4 passivation layer, is mainly utilized to model the device. The simulation of...
This paper describes results of DC characterization in AlGaN/GaN HEMTs passivated with sputter-deposited SiO2, SiN or their multilayered dielectric films. The device with SiO2 passivation exhibited low on-resistance and high breakdown voltage compared to the SiN-passivated device. However, the gate leakage current of the SiO2-passivated device was higher by one order of magnitude than that of the...
This paper describes comparative study of current collapse in AlGaN/GaN high-electron-mobility transistors (HEMTs) passivated with sputter-deposited SiO2 and SiNx dielectrics. The pulsed I-V measurements are employed to characterize switching response of the devices. It is found that the degree of current collapse for the SiNx-passivated device is superior to that for the SiO2-passivated device.
A new HEMT structure is proposed by introducing a low band gap InGaN layer at the heterointerface of an AlGaN/GaN structure. The characteristics of the 2-Dimensional Electron Gas (2DEG) confined in the proposed structure are explored through self-consistent solution of Schrödinger and Poisson's equations. The results show that there is a remarkable improvement in the electron density leading to better...
An effective suppression of drain current collapse was realized in both Enhancement (E)-mode and Depletion (D)-mode AlGaN/GaN High-electron-mobility-transistors (HEMTs) on 4-inch Silicon (111) by ammonium sulfide [(NH4)2Sx] passivation. The current collapse was studied using the pulsed current-voltage characteristics with the pulse width of 200 ns and pulse period of 1 ms. With reference to the AlGaN/GaN...
In situ grown AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) heterostructure field-effect transistor (HFET) is promising for high power applications due to the reduced gate leakage current together with the successful surface passivation. In this study, we present a novel AlGaN/GaN MIS-HFET using in situ AlN as a gate insulator. The AlN is formed subsequently after the epitaxial growth in the same...
In this article, the effect of AlN materials as passivation over AlGaN layer on AlGaN/GaN HEMTs performance was investigated firstly using electro-thermo-mechanical coupled methodology by both TCAD simulation and analytic calculation. It suggested that AlN passivation layer over AlGaN layer effectively spread the surface heat from the channel resulting in reduction of the lattice temperature and enhances...
The blocking characteristics of AlGaN/GaN High-Electron-Mobility Transistors (HEMTs) were considerably improved by an oxygen (O2) annealing. This proposed annealing, which was performed before Schottky contact formation, successfully decreased the leakage current though the buffer region by about six orders of magnitude and had no effect on the current capability of the active region. The suppressed...
We describe the fabrication and characteristics of high voltage enhancement mode SiN/AlGaN/GaN/AlGaN double heterostructure FET devices. The Si3N4 not only acts as a passivation layer but is crucial in the device concept as it acts as an electron donating layer (1). By selective removal under the gate of the in-situ SiN, we realize e-mode operation with a very narrow threshold voltage distribution...
In this paper we have investigated the effectiveness of employing the single field-plate (SFP) technique to enhance the breakdown voltage (BV) of AlGaN/GaN power high electron mobility transistors (HEMTs).A systematic procedure is provided for designing the SFP device, using two dimensional (2-D) simulation to obtain the maximum improvement in the drain-source current (IDS) and to achieve maximum...
We review our state-of-the-art GaN-based device technologies for power switching at low frequencies and high frequency operation aiming at future millimeter-wave communication systems. These two applications are emerging in addition to the widely investigated power amplifiers at microwave frequencies for cellular base stations. As for the power switching GaN devices, we present a novel device structure...
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