Limiting role of dislocations in high-current AlGaN/GaN hot electron transistors

Abstract

III-nitride-based hot electron transistors (HETs) hold significant promise as high-speed, high-power devices. In our previous work, we demonstrated high current density and common-emitter gain at room temperature. Here, we measure multiple devices at cryogenic temperatures, extending the Gummel characteristics past the onset of intervalley scattering at 77 K. We demonstrate a Gummel current gain of 4.7 at a collector current density of 2.6 MA/cm2 at 77 K as well as a peak current density exceeding 3 MA/cm2. From these data, we determine that dislocation-associated inhomogeneities play a limiting role in AlGaN/GaN HETs, controlling the current gain, density, knee voltage, and base-collector leakage. A comparison of two nominally identical devices suggests that even a modest reduction in dislocation density would result in a substantial improvement in HET performance.