A composite field-plated Ga2O3 MOSFET with highly doped ohmic-capping layer is fabricated. An output current of 20 mA mm−1 and on-resistance of 520 mΩ · cm2 shows big improvement upon the previous experiment on similar field plated devices. The breakdown voltage is measured to be 1975 V on an Lgd = 25 μm device. At elevated temperatures, the breakdown voltage decreases to <1 kV at 130 °C, while the on-resistance and saturation current are almost unchanged. The breakdown may be limited by the dielectric liquid strength. The on-resistance is limited by high interface state density that is attributed to the thermal process during the field oxide deposition.
We characterized unintentionally doped β-(Al0.19Ga0.81)2O3 for its structural, band, and electrical properties by using a variety of material and electrical characterization methods such as atom probe tomography (APT), transmission electron microscope, X-ray photoelectron spectroscopy (XPS), capacitance-voltage measurement, and a temperature dependent forward current-voltage measurement. A 115 nm thick β-(Al0.19Ga0.81)2O3 film was grown by molecular beam epitaxy on Sn doped Ga2O3 substrates. Reciprocal space mapping shows a lattice matched (Al0.19Ga0.81)2O3 layer. Both APT and TEM results confirm a sharp β-(Al0.19Ga0.81)2O3/β-Ga2O3 interface. XPS measurements show conduction band offsets of 2.78 ± 0.25 eV and 0.79 ± 0.25 eV between the SiO2/β-(Al0.19Ga0.81)2O3 and β-(Al0.19Ga0.81)2O3/β-Ga2O3 interfaces, respectively. Extracted room temperature Schottky Barrier Heights (SBHs) after zero field correction for Pt, Ni, and Ti were 2.98 ± 0.25 eV, 2.81 ± 0.25 eV, and 1.81 ± 0.25 eV, respectively. The variation of SBHs with metals clearly indicates the dependence on work function.
This Letter reports a high performance β-Ga2O3 thin channel MOSFET with T gate and degenerately doped (n++) source/drain contacts regrown by metal organic chemical vapor deposition. Highly scaled T-gate with a gate length of 160–200 nm was fabricated to achieve enhanced RF performance and passivated with 200 nm silicon nitride. Peak drain current (ID,MAX) of 285 mA/mm and peak transconductance (gm) of 52 mS/mm were measured at 10 V drain bias with 23.5 Ω mm on resistance (RON). Metal/n++ contact resistance of 0.078 Ω mm was extracted from transfer length measurements. RON is possibly dominated by interface resistance between channel and highly doped n++ regrown layer. A gate-to-drain breakdown voltage of 192 V is measured for LGD = 355 nm resulting in average breakdown field (EAVG) of 5.4 MV/cm. This EAVG is the highest reported among all sub-micron gate length lateral FETs. Current gain cut off frequency (fT) of 11 GHz and record power gain cut off frequency (fMAX) of approximately 48 GHz were extracted from small signal measurements. fT is limited by DC-RF dispersion due to interface traps which needs further investigation. The fT·VBR product is 2.112 THz V for 192 V breakdown voltage. Device surpasses the switching figure of merit of Silicon and competitive with mature wide bandgap devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.