High-K Gate Dielectric GaN MOS-HEMTs with Regrown n+ InGaN Source/Drain (Invited Paper)

Due to its high Baliga and Johnson FoMs [1], [2] (Table I), GaN is a promising material for high-voltage power and high frequency, high-power RF applications [3]–[6]. Epitaxial integration of GaN on foreign substrates such as SiC [7]–[14], [30]–[32], sapphire [15], [16], and vastly lattice-mismatched substrates including Si(111) [17]–[24], Si(110) [25], [26], and miscut Si(100) [27]–[29] have already been demonstrated to achieve similarly outstanding mobility, 2DEG charge density and sheet resistance, $\mathrm{R}_{\mathrm{sh}}$ (Fig. 1). Therefore, to realize compact integration of energy-efficient applications such as integrated voltage regulators and RFFE power amplifiers for e.g., in lower power system-on-chip (SoC), it comes down to more than just a choice of the type of substrate, but more importantly, choosing the right transistor architecture. Such a GaN transistor will need to operate in enhancement-mode (e-mode) with low $\mathrm{I}_{\mathrm{OFF}}$ at 0V gate voltage, low gate leakage and provide high performance, i.e., low ON-resistance $(\mathrm{R}_{\mathrm{ON}})$ , high drive current, good RF output power, and power efficiency, all at lower SoC-compatible voltages [31], [32]. As such, high-k gate dielectric is needed to enable low gate leakage in e-mode and scale the oxide $(\mathrm{T}_{\mathrm{oxe}})$ to improve DIBL and $\mathrm{I}_{\mathrm{OFF}}$ , and regrown n+ source/drain is needed for high performance [30]–[32].