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An in situ metal-organic chemical vapor phase epitaxy is used to grow a complete AlGaN/GaN metal oxide semiconductor heterojunction field effect transistor (MOSHFET) structure, gated by a gallium oxide (Ga2O3) layer; we observed reduction in the interfacial trap density compared to its version wherein the Ga2O3 was grown ex situ, after breaking the vacuum, all else being the same. A remarkable decrease in the interfacial charge density for in situ MOSHFET structures in the range of 70%–88% for 10–30 nm oxide layer thickness and improvements in other electrical parameters required for high-performing devices were observed. [ABSTRACT FROM AUTHOR]

The growth of monoclinic phase‐pure gallium oxide (β‐Ga2O3) layers by metal–organic chemical vapor deposition on c‐plane sapphire and aluminum nitride (AlN) templates using silicon‐oxygen bonding (SiOx) as a phase stabilizer is reported. The β‐Ga2O3 layers are grown using triethylgallium, oxygen, and silane for gallium, oxygen, and silicon precursors, respectively, at 700 °C, with and without silane flow in the process. The samples grown on sapphire with SiOx phase stabilization show a notable change from samples without phase stabilization in the roughness and resistivity, from 16.2 to 4.2 nm and from 85.82 to 135.64 Ω cm, respectively. X‐ray diffraction reveals a pure‐monoclinic phase, and Raman spatial mapping exhibits higher tensile strain in the films in the presence of SiOx. The β‐Ga2O3 layers grown on an AlN template, using the same processes as for sapphire, show an excellent epitaxial relationship between β‐Ga2O3 and AlN and have a significant change in β‐Ga2O3 surface morphology. [ABSTRACT FROM AUTHOR]

We report the electrical properties of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) structures with a Ga2O3 passivation layer grown by metal–organic chemical vapor deposition (MOCVD). In this study, three different thicknesses of β-Ga2O3 dielectric layers were grown on Al0.3Ga0.7N/GaN structures leading to metal-oxide-semiconductor-HFET or MOSHFET structures. X-ray diffraction (XRD) showed the ( 2 ¯ 01) orientation peaks of β-Ga2O3 in the device structure. The van der Pauw and Hall measurements yield the electron density of ~ 4 × 1018 cm−3 and mobility of ~770 cm2V−1s−1 in the 2-dimensional electron gas (2DEG) channel at room temperature. Capacitance–voltage (C-V) measurement for the on-state 2DEG density for the MOSHFET structure was found to be of the order of ~1.5 × 1013 cm−2. The thickness of the Ga2O3 layer was inversely related to the threshold voltage and the on-state capacitance. The interface charge density between the oxide and Al0.3Ga0.7N barrier layer was found to be of the order of ~1012 cm2eV−1. A significant reduction in leakage current from ~10−4 A/cm2 for HFET to ~10−6 A/cm2 for MOSHFET was observed well beyond pinch-off in the off-stage at -20 V applied gate voltage. The annealing at 900° C of the MOSHFET structures revealed that the Ga2O3 layer was thermally stable at high temperatures resulting in insignificant threshold voltage shifts for annealed samples with respect to as-deposited (unannealed) structures. Our results show that the MOCVD-gown Ga2O3 dielectric layers can be a strong candidate for stable high-power devices. [ABSTRACT FROM AUTHOR]

We report a comparative spectroscopic study on the thin films of epitaxial aluminum nitride (AlN) on basal plane sapphire (Al2O3) substrates grown in hydrogen (H2) and nitrogen (N2) gas reaction environments. AlN films of similar thicknesses (~3.0 µm) were grown by metal-organic chemical vapor deposition (MOCVD) for comparison. The impact of the gas environment on the AlN epilayers was characterized using high-resolution X-ray diffraction (HR-XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering (RS), secondary ion mass spectroscopy (SIMS), cathodoluminescence (CL), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The study showed that AlN layers grown in a N2 environment have 50% less stress (~0.5 GPa) and similar total dislocation densities (~109/cm2) as compared to the films grown in a H2 environment. On the other hand, AlN films grown in a H2 gas environment have about 33% lesser carbon and 41% lesser oxygen impurities than films grown in a N2 growth environment. The possible mechanisms that influenced the structural quality and impurity incorporation for two different gas environments to grow AlN epilayers in the MOCVD system on sapphire substrates were discussed. [ABSTRACT FROM AUTHOR]

We report an Ultrawide Bandgap Al0.4Ga0.6N channel metal-oxide-semiconductor heterostructure field effect transistor with drain currents exceeding 1.33 A mm−1 (pulse) and 1.17 A mm−1 (DC), around a 2-fold increase over past reports. This increase was achieved by incorporating a hybrid barrier layer consisting of an AlN spacer, n-doped Al0.6Ga0.4N barrier and a thin reverse graded AlxGa1–xN (x from 0.60 to 0.30) cap layer. To enhance current spreading, a "perforated" channel layout comprising of narrow channel sections separated by current blocking islands was used. A composite ALD deposited ZrO2/Al2O3 film was used as gate dielectric. A breakdown field above 2 MV cm−1 was measured. [ABSTRACT FROM AUTHOR]

Ultrawide bandgap (UWBG) AlGaN-channel metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with a ZrO2 gate dielectric achieve peak current in excess of 0.4 A/mm and current ON/OFF ratios >106 with subthreshold swings as low as 110 mV/decade. These devices have strong potential for use in power and radio frequency electronics or as true solar-blind photodetectors. In this work, we present the photoresponse analysis in UWBG AlGaN MOSHFETs. Persistent photoconductivity with the decay time above 10 minutes can be quenched by illuminating with strong UV light at 365 nm and 254 nm, suggesting deep traps to be responsible for this behavior. Upon correlating the optical response under various illumination conditions with cathodoluminescence of these devices, we identified two key trap levels at ∼2.48 ± 0.14 eV and 3.76 ± 0.06 eV, controlling the slow response time. By depth-profiling using cathodoluminescence, these traps are identified to be at the AlN/AlGaN interface at the back of the device, due to partial relaxation from the lattice mismatch between AlN and Al0.4Ga0.6N. [ABSTRACT FROM AUTHOR]