Abstract
AlGaN/GaN fin-shaped and large-area grating gate transistors with two layers of two-dimensional electron gas and a back gate were fabricated and studied experimentally. The back gate allowed reducing the subthreshold leakage current, improving the subthreshold slope and adjusting the threshold voltage. At a certain back gate voltage, transistors operated as normally-off devices. Grating gate transistors with a high gate area demonstrated little subthreshold leakage current, which could be further reduced by the back gate. The low frequency noise measurements indicated identical noise properties and the same trap density responsible for noise when the transistors were controlled by either top or back gates. This result was explained by the tunneling of electrons to the traps in AlGaN as the main noise mechanism. The trap density extracted from the noise measurements was similar or less than that reported in the majority of publications on regular AlGaN/GaN transistors.
Highlights
Aluminum gallium nitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) are already commercialized and are widely used in high-power switching and high-frequency applications
In spite of the extremely high gate area, transistors demonstrated small subthreshold leakage current, which is a requirement for high frequency experiments
The subthreshold leakage current can be further reduced by the back gate voltage
Summary
Aluminum gallium nitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) are already commercialized and are widely used in high-power switching and high-frequency applications. Double-channel, high electron mobility structures with top grating gates have demonstrated a number of new effects at terahertz frequencies, which are promising for detectors, intensity modulators and filters [19,20]. These devices have to have large active areas, orders of magnitude larger than those of "standard" field effect transistors. This poses a serious challenge for fabricating such devices with low gate leakage current. It was shown that the back gate reduces the gate leakage current
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