Low-Frequency Noise in SiO 2 /AlGaN/GaN Heterostructures on SiC and Sapphire Substrates
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Department of ECSE, Rensselaer Polytechnic Institute, Troy, New York 12180, USA Department of ECE, University of South Carolina, Columbia, South Carolina 29208, USA 2
ABSTRACT The low-frequency noise in GaN-based Metal-Oxide-Semiconductor Heterostructure Field Effect Transistors (MOS-HFETs) and HFETs on sapphire and nSiC substrates were studied. Hooge parameter at zero gate bias was calculated about 8 x 10-4 for both types of the devices. The AlGaN/GaN MOS-HFETs exhibited extremely low gate leakage current and much lower noise at both positive and negative gate biases. These features demonstrate the high quality of the SiO2/AlGaN heterointerface and feasibility of this technology for high-power microwave transmitter and high-power, high-temperature switches.
INTRODUCTION Heterostructure Field Effect Transistors (HFETs) based on AlGaN/GaN material system are expected to offer superior performance in microwave and optical communication systems [1,2]. AlGaN/GaN HFETs grown on sapphire and silicon carbide substrates with impressive DC and microwave characteristics demonstrated [3,4].It is important to know the low frequency noise since it is the limiting figure for all kinds of HEMTs and MOSFETs. Especially when these devices are used as oscillators or mixers, low-frequency noise limits the phase-noise characteristics and degenerates the performance of the electronic system. It was shown that the level of the low frequency noise strongly depends on the gate leakage current Ig even at Ig/ Id
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