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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. 

We demonstrated a metal-organic chemical vapor deposition (MOCVD) of smooth, thick, and monoclinic phase-pure gallium oxide (Ga2O3) on c-plane sapphire using silicon-oxygen bonding (SiOx) as a phase stabilizer. The corundum (α), monoclinic (β), and orthorhombic (ε) phases of Ga2O3 with a bandgap in the 4.4 – 5.1 eV range, are promising materials for power semiconductor devices and deep ultraviolet (UV) solar-blind photodetectors. The MOCVD systems are extensively used for homoepitaxial growth of β-Ga2O3 on (001), (100), (010), and (¯2 01) β-Ga2O3 substrates. These substrates are rare/expensive and have very low thermal conductivity; thus, are not suitable for high-power semiconductor devices. The c-plane sapphire is typically used as a substrate for high-power devices. The β-Ga2O3 grows in the (¯2 01) direction on sapphire. In this direction, the presence of high-density oxygen dangling bonds, frequent stacking faults, twinning, and other phases and planes impede the heteroepitaxy of thick β-Ga2O3. Previously phase stabilizations with SiOx have been reported for tetragonal and monoclinic hafnia. We were able to grow ~580nm thick β-Ga2O3 on sapphire by MOCVD at 750 oC through phase stabilization using silane. The samples grown with silane have a reduction in the surface roughness and resistivity from 10.7 nm to 4.4 nm and from 371.75 Ω.cm to 135.64 Ω.cm, respectively. These samples show a pure-monoclinic phase determined by x-ray diffraction (XRD); have tensile strain determined by Raman strain mapping. These results show that a thick, phase-pure -Ga2O3 can be grown on c-plane sapphire which can be suitable for creating power devices with better thermal management. 

We report the gate leakage current and threshold voltage characteristics of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) with metal-organic chemical vapor deposition (MOCVD) grown β-Ga2O3 as a gate dielectric for the first time. In this study, GaN channel HFET and β-Ga2O3 passivated metal-oxide-semiconductor-HFET (MOS-HFET) structures were grown in MOCVD using N2 as carrier gas on a sapphire substrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to characterize the structural properties and surface morphology of the heterostructure. The electrical properties were analyzed using van der Pauw, Hall, and the mercury probe capacitance-voltage (C-V) measurement systems. The 2-dimensional electron gas (2DEG) carrier density for the heterostructure was found to be in the order of ~1013 cm-2. The threshold voltage shifted more towards the negative side for the MOSHFET. The high-low (Hi-Lo) frequency-based C-V method was used to calculate the interface charge density for the oxide-AlGaN interface and was found to be in the order of ~1012 cm2eV-1. A remarkable reduction in leakage current from 2.33×10-2 A/cm2 for HFET to 1.03×10-8 A/cm2 for MOSHFET was observed demonstrating the viability of MOCVD-grown Ga2O3 as a gate dielectric. 

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. 

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 (SiO_x) as a phase stabilizer is reported. The β‐Ga₂O₃layers 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 SiO_xphase 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 SiO_x. The β‐Ga₂O₃layers grown on an AlN template, using the same processes as for sapphire, show an excellent epitaxial relationship between β‐Ga₂O₃and AlN and have a significant change in β‐Ga₂O₃surface morphology. 

Titanium nitride (TiN) is highly attractive for plasmonics and nanophotonics applications owing to its gold‐like but tunable optical properties. Its prodigious potential for plasmonics has been demonstrated on sapphire or bulk MgO. For a transformational impact, high optical quality TiN on Si is required instead, which would support the integration of nanophotonics with the complementary metal‐oxide‐semiconductor (CMOS) electronics. However, TiN grown on Si, even at elevated temperatures, lacks the optical quality needed, imposed by the large lattice mismatch between them. Here, a novel approach is reported wherein a thin MgO interlayer is inserted between TiN and Si. The improved crystalline quality enabled by MgO for TiN on Si(001) leads to a significant enhancement of the plasmonic figure of merit (FOM = −ε′/ε″) from 2.0 to 2.5 at telecommunication wavelength (peak FOM of 2.8), which is comparable to the widely accepted ultimate FOM obtained on bulk MgO grown under similar conditions. The TiN/MgO/Si structure enables the hybrid‐plasmonic‐photonic waveguide platform with sufficiently low losses, and thus long propagation lengths, for nanophotonic devices while providing additional practical advantages such as serving as a self‐aligned robust etching mask. Thus, the much‐anticipated potential of TiN on Si platform for CMOS compatible plasmonics is brought closer to reality.