We discuss an AlGaN/GaN metal–semiconductor field-effect transistor (MESFET) structure grown without any impurity doping in the channel. A high-mobility polarization-induced bulk channel charge was created by grading the channel region linearly from GaN to over 1000 Å. This polarization-doped FET (PolFET) was fabricated and tested under dc and rf conditions. Current density of 850 mA/mm and transconductance of 93 mS/mm was observed under dc conditions. The 0.7 μm gate length devices had a cutoff frequency, and maximum oscillation frequency, We demonstrate that the PolFETs perform better than comparable MESFETs with impurity-doped channels, and are suitable for high power microwave applications. An important advantage of these devices over AlGaN/GaN high electron mobility transistors is that the transconductance versus gate voltage profile can be tailored by compositional grading for better large-signal linearity.
AlGaN/GaN polarization-doped field-effect transistor for microwave power applications
Siddharth Rajan, Huili Xing, Steve DenBaars, Umesh K. Mishra, Debdeep Jena; AlGaN/GaN polarization-doped field-effect transistor for microwave power applications. Appl. Phys. Lett. 1 March 2004; 84 (9): 1591–1593. https://doi.org/10.1063/1.1652254
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