Development of GaAs-based MOSFET using molecular beam epitaxy

Enhancement mode, high electron mobility PHEMT-based metal oxide semi conductor field effect transistor (MOSFET) devices have been fabricated using an oxide high-κ gate dielectric stack developed using molecular beam epitaxy. A template layer of Ga2O3, initially deposited on the surface of the III-V device unpins the GaAs Fermi level while the deposition of a bulk ternary (GdxGa1-x)2O3 layer forms the highly resistive layer to reduce leakage current through the dielectric stack. The use of molecular beam epitaxy allows for the control and uniformity of the oxide layers along the growth direction and deposition conditions were optimized for oxide surface morphology and interface quality. A midgap interface state density for the high-κ stack on GaAs of ≅2×1011cm-2eV-1 and a dielectric constant of κ≅20 are determined using electrical measurements. Enhancement-mode n-channel MOSFETs with a gate length of 1μm and a source-drain spacing of 3μm show a threshold voltage, saturation current, transconductance, and on-resistance of 0.11 V, 380mAmm-1, 250mSmm-1, and 4.5Ωmm, respectively.