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The energy band alignment of the atomic-layer-deposited In2O3/β-Ga2O3 ( 2 ¯ 01 ) interface is evaluated by X-ray photoelectron spectroscopy. The X-ray diffraction pattern reveals that the In2O3 film grown at 160 °C is amorphous, while it becomes polycrystalline at a higher deposition temperature of 200 °C. The bandgaps, determined by reflection electron energy loss spectroscopy, are 4.65, 3.85, and 3.47 eV for β-Ga2O3, polycrystalline In2O3, and amorphous In2O3, respectively. Both amorphous and polycrystalline In2O3/β-Ga2O3 interfaces have Type I alignment. The conduction and valence band offsets at the polycrystalline (amorphous) In2O3/β-Ga2O3 interface are 0.35 and 0.45 eV (0.39 and 0.79 eV), respectively. These observations suggest that polycrystalline In2O3 as an intermediate semiconductor layer is beneficial to the barrier reduction of metal/Ga2O3 contact. [ABSTRACT FROM AUTHOR]

The pH-concentration diagram for the formation of barium molybdate films on a metallic molybdenum substrate in a barium hydroxide aqueous solution has been experimentally studied. Due to the relatively large solubility of the molybdate, the estimation of film thickness from the weight gain was corrected by considering the substrate dissolution. The molybdenum substrates had a preferential [100] crystallographic orientation, but the films exhibited no preferential orientation. It is suggested that the film grows through a dissolution-precipitation mechanism and that nucleation begins only after the solution is locally saturated with barium molybdate. Irregular intergrowth is frequent due to the high crystal growth rate. XPS measurements on samples that appeared completely coated under SEM examination exhibited only the peaks corresponding to barium molybdate. On the other hand, the substrates that appeared partially coated under SEM, when examinated by XPS exhibited the superposition of spectra of the molybdate and of the uncoated molybdenum substrate. This allows the study of the degree of coating as a function of the solution concentration and pH. [Copyright &y& Elsevier]

Hybrid heterojunctions based on two-dimensional (2D) and conventional three-dimensional (3D) materials provide a promising way toward nanoelectronic devices with engineered features. In this work, we investigated the band alignment of a mixed-dimensional heterojunction composed of transferred MoS2 on β-Ga2O3( 2 - 01) with and without nitridation. The conduction and valence band offsets for unnitrided 2D-MoS2/3D-β-Ga2O3 heterojunction were determined to be respectively 0.43 ± 0.1 and 2.87 ± 0.1 eV. For the nitrided heterojunction, the conduction and valence band offsets were deduced to 0.68 ± 0.1 and 2.62 ± 0.1 eV, respectively. The modified band alignment could result from the dipole formed by charge transfer across the heterojunction interface. The effect of nitridation on the band alignments between group III oxides and transition metal dichalcogenides will supply feasible technical routes for designing their heterojunction-based electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Ultra-wide bandgap beta-gallium oxide (β-Ga2O3) has been attracting considerable attention as a promising semiconductor material for next-generation power electronics. It possesses excellent material properties such as a wide bandgap of 4.6-4.9 eV, a high breakdown electric field of 8 MV/cm, and exceptional Baliga’s figure of merit (BFOM), along with superior chemical and thermal stability. These features suggest its great potential for future applications in power and optoelectronic devices. However, the critical issue of contacts between metal and Ga2O3 limits the performance of β-Ga2O3 devices. In this work, we have reviewed the advances on contacts of β-Ga2O3 MOSFETs. For improving contact properties, four main approaches are summarized and analyzed in details, including pre-treatment, post-treatment, multilayer metal electrode, and introducing an interlayer. By comparison, the latter two methods are being studied intensively and more favorable than the pre-treatment which would inevitably generate uncontrollable damages. Finally, conclusions and future perspectives for improving Ohmic contacts further are presented. [ABSTRACT FROM AUTHOR]

We demonstrate a diode-pumped passively cw mode-locked Nd:CaGdAlO4 laser operating at 1079nm with a semiconductor saturable absorber mirror for the first time to the best of our knowledge. The threshold pump power of the laser is 180mW. A maximum average output power of 93mW is obtained under the pump power of 1.94 W. The pulse duration of the mode-locked pulses is 3.1 ps and the repetition rate is 157 MHz. [ABSTRACT FROM AUTHOR]

β-Ga 2 O 3 is considered an attractive candidate for next-generation high-power electronics due to its large band gap of 4.9 eV and high breakdown electrical field of 8 MV/cm. However, the relatively low carrier concentration and low electron mobility in the β-Ga 2 O 3 -based device limit its application. Herein, the high-quality β-Ga 2 O 3 single crystal with high doping concentration of ∼3.2 × 10 19 cm -3 was realized using an optical float-zone method through Ta doping. In contrast to the SiO 2 /β-Ga 2 O 3 gate stack structure, we used hexagonal boron nitride as the gate insulator, which is sufficient to suppress the metal-insulator-semiconductor (MIS) interface defects of the β-Ga 2 O 3 -based MIS field-effect transistors (FETs), exhibiting outstanding performances with a low specific on-resistance of ∼6.3 mΩ·cm 2 , a high current on/off ratio of ∼10 8 , and a high mobility of ∼91.0 cm 2 /(V s). Our findings offer a unique perspective to fabricate high-performance β-Ga 2 O 3 FETs for next-generation high-power nanoelectronic applications.

For the first time, we report the successful fabrication of well-behaved field-effect transistors based on Nb-doped β-Ga 2 O 3 nanobelts mechanically exfoliated from bulk single crystals. The exfoliated β-Ga 2 O 3 nanobelts were transferred onto a purified surface of the 110 nm SiO 2 /Si substrate. These Nb-doped devices showed excellent electrical performance such as an ultrasmall cutoff current of ∼10 fA, a high current on/off ratio of >10 8 , and a quite steep subthreshold swing (SS, ∼120 mV/decade). Furthermore, we investigated the temperature dependence down to 200 K, providing insightful information for its operation in a harsh environment. This work lays a foundation for wider application of Nb-doped β-Ga 2 O 3 in nano-electronics.