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For the first time, a core drain current model based on surface potential without any implicit functions is developed for beta-phase gallium oxide (β-Ga2O3) power metal-oxide-semiconductor field-effect transistors (MOSFETs). The surface potential solution is analytically deduced by solving the Poisson equation with appropriate simplification assumptions in accumulation, partial-depletion, and full-depletion modes. Then, the drain current expression is analytically derived from the Pao–Sah integral as a function of the mobile charge density obtained from the surface potential at the source and drain terminals. In addition, nonlinear resistors in the source/drain access region are considered. It continuously predicts the characteristics of β-Ga2O3 power MOSFETs in all operation modes, including accumulation mode, partial-depletion mode, and full-depletion mode. Furthermore, the validity of the model is verified by comparing the results of the model with the numerical simulations carried out with the technology computer-aided design (TCAD) tool ATLAS Device Simulator from Silvaco. Good agreement between the proposed model and TCAD simulations is shown for β-Ga2O3 power MOSFETs with different intrinsic channel lengths, channel doping concentrations, and channel thicknesses. Ultimately, the Gummel symmetry test and the harmonic balance simulation test are performed to validate the model's robustness and convergence. [ABSTRACT FROM AUTHOR]

Vertical metal–oxide–semiconductor field effect transistor (MOSFET) is essential to the future application of ultrawide bandgap β-Ga2O3. In this work, we demonstrated an enhancement-mode β-Ga2O3 U-shaped gate trench vertical metal–oxide–semiconductor field effect transistor (UMOSFET) featuring a current blocking layer (CBL). The CBL was realized by high-temperature annealing under oxygen ambient, which provided electrical isolation between the source and drain electrodes. The CBL thicknesses of different annealing temperatures were derived from C–V measurements and the Fermi level position of the sample surfaces of different annealing temperature was characterized by x-ray photoelectron spectroscopy measurements, indicating good process controllability. Furthermore, photoluminescence spectra were measured to study the effect of oxygen annealing. The fabricated UMOSFET showed normally off with a Vth of 11.5 V, an on-state resistance of 1.48 Ω cm2, a maximum on-state current of 11 A/cm2, an on–off ratio of 6 × 104, and a three-terminal breakdown voltage over 100 V. This work paves a way to form a CBL and broadens the design space for high-power β-Ga2O3 vertical transistors. [ABSTRACT FROM AUTHOR]

A $\beta $ -Ga2O3 MOSFET is fabricated and its threshold voltage $({V}_{\mathrm{TH}})$ instability mechanisms are experimentally investigated under different gate-biased voltages and ambient temperatures. Under the condition of the positive bias stress (PBS) of ${V}_{\mathrm{GS}} = 4$ V for 1000 s at room temperature, the ${V}_{\mathrm{TH}}$ positive shift of 0.61 V is mainly caused by the electrons trapped by border traps in Al2O3. Combining the hysteresis with temperature-dependent performance analysis, the clockwise to anticlockwise hysteresis inversion at 125 °C is discovered in $\beta $ -Ga2O3 MOSFET for the first time, which is probably caused by the activation of deep-level acceptor-type interface states. The deep-level acceptor-type interface states with a fitting activation energy of 114 meV are found, and they also affect the ${V}_{\mathrm{TH}}$ instability at high temperature. With the stress of ${V}_{\mathrm{GS}} =4$ V at 125 °C for 1000 s, ${V}_{\mathrm{TH}}$ is increased by 0.9 V. Analyzing electrical parameters, such as ${V}_{\mathrm{TH}}$ , subthreshold slope (SS), and hysteresis width, can distinguish the quantitative contributions of interface states and border traps to ${V}_{\mathrm{TH}}$ instability under electrical stress and thermal stress (TS). This work reveals an important indication for investigating the ${V}_{\mathrm{TH}}$ instability of $\beta $ -Ga2O3 MOSFET in high-power applications. [ABSTRACT FROM AUTHOR]

High tunability of photoresponse characteristics under work conditions is desired for a single solar-blind photodetector to be applied in multifarious fields. Three-terminal metal–oxide–semiconductor field-effect phototransistors have shown excellent controllability of performance, but the hysteresis issue impedes their stable operation. In this work, the metal–semiconductor field-effect phototransistor based on the exfoliated Ga2O3 microflake and graphene thin film is demonstrated. The high-quality quasi-van der Waals interface between Ga2O3 and graphene eliminates the hysteresis issue and generates a subthreshold swing as low as 69.4 mV/dec. By regulating gate voltage (Vg), the dominated mechanism of photocurrent generation in the device can be tuned continuously from the fast photoconduction effect to photogating effect with high photogain. Accordingly, the responsivity, dark current, detectivity, rejection ratio, and decay time of the device can be well adjusted by the Vg. At Vg = −1 V and a source to drain voltage of 2 V, the device shows excellent performance with a responsivity of 2.82 × 103 A/W, a rejection ratio of 5.88 × 105, and a detectivity of 2.67 × 1015 Jones under 254 nm illumination. This work shows the possibility of realizing highly tunable solar-blind photodetectors to meet the requirements for different application fields by introducing gate voltage modulation. [ABSTRACT FROM AUTHOR]

In this article, for the first time, a variation of lateral doping (VLD) technique was proposed to improve blocking voltage and ON-resistance properties in the lateral β-Ga2O3 metal–oxide–semiconductor field-effect transistor (MOSFET). Enhancement-mode operation was achieved in the VLD transistor. The maximum transconductance of this new device is more than three times as large as the uniformly doped (UD) transistor. Moreover, the OFF-state electric field at the channel was suppressed compared to the UD transistor, resulting in higher blocking voltage. We also investigated the optimal device properties with changing channel concentration in the drift region of VLD transistor. A power figure of merit of 332.7 MW/cm2 was reached by VLD design. Thus, this proposed structure provides a new design strategy for high-power β-Ga2O3 MOSFETs. [ABSTRACT FROM AUTHOR]

Herein, high‐performance enhancement‐mode (E‐mode) β‐Ga2O3 metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) are achieved on Si‐doped homoepitaxial films. Oxygen annealing (OA) treatment under the gate region is used to effectively exhaust the channel electron, resulting in the normally off operation of the device. The threshold voltage, defined as that at the drain current of 0.1 mA mm−1, for the fabricated device is extracted to be 4.1 V. Moreover, double source‐connected field plates are used to suppress the peak electric fields in both Ga2O3 channel and SiNx passivation layer. The fabricated β‐Ga2O3 MOSFETs with gate‐to‐drain distance (Lgd) of 17 μm exhibit a record high breakdown voltage over 3000 V. It is shown that the OA treatment is a new way to obtain high‐performance E‐mode β‐Ga2O3 power MOSFETs. [ABSTRACT FROM AUTHOR]

In this letter, trench-gate metal–oxide–semiconductor field-effect transistors on (010) $\beta $ -Ga2O3 epitaxial layer are fabricated. Enhancement mode is achieved by the gate-recess process, through thoroughly depleting the $\beta $ -Ga2O3 channel to get a positive threshold voltage. For the first time, by using a dynamic parameter test system, the Ga2O3 MOSFET with 2- $\mu \text{m}$ gate length is characterized to present short switching time, including turn-on time ($\textit {t}_{ \mathrm{\scriptscriptstyle ON}}$) of 28.6 ns and turn-off time ($\textit {t}_{ \mathrm{\scriptscriptstyle OFF}}$) of 94.0 ns. In addition, OFF-state interelectrode parasitic capacitances, including input capacitance ($\textit {C}_{\text {iss}}$) of 37 pF/mm, output capacitance ($\textit {C}_{\text {oss}}$) of 42 pF/mm, and reverse transfer capacitance ($\textit {C}_{\text {rss}}$) of 14 pF/mm are also obtained, which can account for the high switching speed. The static and dynamic switching properties of the trench-gate device show the potential of $\beta $ -Ga2O3 MOSFET for the high-speed switching applications. [ABSTRACT FROM AUTHOR]

An enhancement-mode $\beta $ -Ga2O3 metal–oxide–semiconductor field-effect solar-blind phototransistor on Si-doped homoepitaxial film grown by molecular beam epitaxy is demonstrated in this letter. Gate-recess process was employed to fully deplete the Ga2O3 channel to achieve positive threshold voltage ${V}_{{\textsf {th}}}$ (7 V), which broadens the operating range of the solar-blind phototransistor. The dark current of about 0.7 pA is extremely low. Under 254-nm light illumination of 63 $\mu \text{W}$ /cm2, the change of drain current reaches more than 6 orders of magnitude. Record high detectivity of 1.3 $\boldsymbol {\times }\,\,10^{{\textsf {16}}}$ Jones and photo-to-dark current ratio of $1.1\,\,{\boldsymbol {\times }}\,\,10^{{\textsf {6}}}$ are obtained, respectively. In addition, the rise and decay time are as short as 100 and 30 ms, respectively. High responsivity of $3\,\,\boldsymbol {\times }\,\, 10^{{\textsf {3}}}$ A/W and external quantum efficiency of $1.5\,\,\boldsymbol {\times }\,\,10^{{\textsf {6}}}$ % are also achieved with apparent solar-blind photodetection. [ABSTRACT FROM AUTHOR]

In this letter, source-field-plated $\beta $ -Ga2O3 MOSFETs are fabricated on Si-doped homoepitaxial film on (010) Fe-doped semi-insulating $\beta $ -Ga2O3 substrate. Ohmic contact resistance (${R}_{\textsf {c}}$) between metal- and ion-implanted source/drain layer of $1.0~\Omega ~\cdot $ mm is obtained by employing the Si-ion implantation. The fabricated source-field-plated $\beta $ -Ga2O3 MOSFETs with source-to-drain distance (${L}_{\textsf {sd}}$) of 11 and $18~\mu \text{m}$ present high-saturation drain current (${I}_{\textsf {ds,sat}}$) of 267 and 222 mA/mm with low ${R}_{\textsf {on,sp}}$ of 4.57 and 11.7 $\text{m}\Omega ~\cdot $ cm2, respectively. The drain extension in the source-field plate effectively suppresses the peak electric field and improves the breakdown voltage greatly. The destructive breakdown voltages (${V}_{\textsf {br}}$) are measured to be 480 and 680 V for the devices with ${L}_{\textsf {sd}}$ of 11 and 18 $\mu \text{m}$ , respectively. Most of all, the power figure of merit (${V}_{\textsf {br}}^{\textsf {2}}/{R}_{\textsf {on,sp}})$ is as high as 50.4 MW/cm2, which is the highest value among any $\beta $ -Ga2O3 MOSFETs ever reported. [ABSTRACT FROM AUTHOR]