The Ambient Temperature Effect on Current-Voltage Characteristics of Surface-Passivated GaN-Based Field-Effect Transisto
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Internet Journal Nitride Semiconductor Research
The Ambient Temperature Effect on Current-Voltage Characteristics of Surface-Passivated GaN-Based Field-Effect Transistors W.L. Liu1, V.O. Turin1, A.A. Balandin1, Y.L. Chen2 and K.L. Wang2 1Nano-Device 2Device
Laboratory, Department of Electrical Engineering, University of California - Riverside, Research Laboratory,Electrical Engineering Department,University of California - Los Angeles.,
(Received Friday, September 3, 2004; accepted Friday, November 19, 2004)
We have studied experimentally the effect of ambient temperature on performance of the surfacepassivated Al0.2Ga0.8N/GaN heterostructure field-effect transistors in the temperature range from 25°C to 250°C. The measured data have been compared with physics-based modeling of the GaN transistor characteristics under different ambient temperatures. The experimental data, showing about 33% degradation in the saturation current with a temperature increase from 25°C to 250°C, agrees well with the results of simulations performed using ISE DESSIS software. Obtained results and analytical extrapolations can be used for predicting device performance in changing environments, as well as for optimization of the device structure.
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Introduction
GaN-based heterostructure field-effect transistors (HFETs) are attracting attention as promising candidates for high-frequency high-power applications. AlGaN/GaN HFETs have demonstrated the ability to operate at frequencies above 10 GHz while providing power levels exceeding 11 W/mm [1] [2]. These devices are capable of working with low flicker noise levels
vapor deposition technology. The structure consists of 1.2 µm undoped GaN, 50 nm undoped GaN channel layer, 3 nm undoped Al0.2Ga0.8N spacer and 15 nm Si
(Hooge parameter αH 10-4~10-5) comparable to those in Si and GaAs devices [3] [4]. For applications in remotely controlled vehicles and satellites, the stability of device operation under changing temperature is of critical importance. An increase in ambient temperature coupled with strong self-heating effects in high-power GaN transistors may result in significant performance degradation. The thermal structure resistance also increases at high temperature due to the decrease of the thermal conductivity K, which falls off as ~ 1/T0.5 in GaN films [5] [6] [7]. In this paper we report results of experimental investigation and computer simulation of the effect of ambient temperature on performance of the SiO2-passivated Al0.2Ga0.8N/GaN HFETS.
doped (ND=6×1018cm-3) Al0.2Ga0.8N barrier layers. HFETs with gate dimension of 1 µm × 20 µm, and the gate-source and gate-drain distances of 1 µm have been fabricated on this heterostructure. Mesa isolation is achieved by ion implantation of As+ at 75 keV and dose1.27×1011 cm2, As+ at 375 keV and dose 4.32×1011 cm2, and He+ at 75 keV and dose 5.43×1011 cm2. The source - drain ohmic contacts are formed by Ti/Al/Ni/ Au (200Å /800Å /400Å /1500Å) multilayer. The gate Schottky contact is formed by Pd/Au (200Å/6500Å) layer. Before metal dep
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