GaN-Based Field-Effect Transistors With Laterally Gated Two-Dimensional Electron Gas

In this letter, we report on GaN-based field-effect transistors with laterally gated two-dimensional electron gas (2DEG). The drain current of the transistor is controlled solely by modulating the width of the 2DEG between buried gates. The lateral Schottky gate contact to the GaN channel layer enhances electron confinement by raising electrostatic potential below the 2DEG, improving isolation between the source and drain. Complete elimination of a top-contact gate reduces the density of trapped electrons near the surface and alleviates capacitive coupling between the trapped electrons and the 2DEG. Owing to the unique device structure and operation principle, the 150-nm-gate transistors with a channel width of 250 nm demonstrated: extremely small output conductance, drain-induced barrier lowering, knee voltage, and knee current collapse, greatly reduced gm derivatives near threshold, and nearly constant RF gain along the resistive load line. Furthermore, a preliminary accelerated life test indicated enhanced device reliability due to an absence of the inverse piezoelectric effect. The proposed transistors hold great promise for realizing reliable and efficient power amplifiers with improved transistor linearity.