Secondary Effects in Electrical Behavior of Body-Diode Integrated AlGaN/GaN HEMTS

Abstract

We have recently demonstrated dual-gate control in AlGaN/GaN high electron mobility transistors (HEMTs) with the integration of body-diode based back-gate [1]. To integrate body-diode, conventional AlGaN/GaN HEMT structure is grown on a p-GaN layer and a back-gate terminal is connected to the underlying p-GaN layer. This design allows the back-gate voltage to control the depletion width of the body-diode, which in turn modulates the two-dimensional electron gas (2DEG) density at the AlGaN/GaN interface. A positive/negative shift in the threshold voltage is obtained by increasing/decreasing the depletion width of the body-diode with the application of back-gate voltage. With dual gate control, we have successfully demonstrated shift in the threshold voltage of a normally-ON HEMT towards normally-OFF mode along with improved breakdown voltage. Here we present, observations of secondary effects in the integrated body-diode AlGaN/GaN HEMT device structure. Secondary effects are investigated under both biased and floating back-gate conditions [2]. Our results show that, at higher drain voltages, bias at the drain terminal plays a crucial role in biasing the body-diode under dynamic operation. Secondary effects such as kink-effect in the saturation channel current and light emission under the source terminal are observed under dynamic operation. We will further discuss the effect of parasitic bipolar junction transistor (BJT) formation on the device performance in this integrated device configuration.