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[IEEE 2018 76th Device Research Conference (DRC) - Santa Barbara, CA, USA (2018.6.24-2018.6.27)] 2018 76th Device Research Conference (DRC) - 710 V Breakdown Voltage in Field Plated Ga203 MOSFET
摘要： ?-Gallium oxide (Ga2O3) is an increasingly attractive choice for next generation power electronics applications due to its high Baliga’s figure of merit (BFoM) and mature bulk substrate growth technologies. Recent experiments have shown its great potential as the next generation power semiconductor. There have been reports on MOSFETs with breakdown of 750 V[1], large on current densities exceeding 1.5 A/mm [2], and enhancement mode operation by interface state modulation [3]. In order to increase the breakdown voltage of ??Ga2O3 MOSFETs, the electric field needs to be reduced in the gate oxide and air near the gate-drain region; breakdown could occur in these regions before the intrinsic Ga2O3 breakdown in the channel. In this report, we design a composite ALD/PECVD field plate to increase the breakdown voltage of Ga2O3 MOSFETs achieving a maximum breakdown voltage of 710 V. The comparison between field plate and non-field plate devices suggest breakdown outside the channel and field plate oxide region, indicating the channel is still far from breakdown condition.
关键词： Ga2O3,MOSFET,breakdown voltage,power electronics,field plate
更新于2025-09-09 09:28:46
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β-Ga2O3:Ce as a fast scintillator: An unclear role of cerium
摘要： β-Ga2O3 and β-Ga2O3:Ce crystals have been grown by the Czochralski method and their scintillation properties have been studied by means of pulse height, radioluminescence and scintillation time profile measurements. It is shown that although the scintillation of β-Ga2O3:Ce is related to intrinsic excitonic emission, the doping with Ce improves some characteristics of the material. The prominent samples of β-Ga2O3:Ce display fast 6 ns (40%) scintillation, with total light yields of about 5000 ph/MeV.
关键词： scintillation,scintillation decay,β-Ga2O3 crystal,Ce-doped β-Ga2O3 crystal,radioluminescence
更新于2025-09-04 15:30:14
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Three-dimensional anisotropic thermal conductivity tensor of single crystalline β-Ga <sub/>2</sub> O <sub/>3</sub>
摘要： β-Ga2O3 has attracted considerable interest in recent years for high power electronics, where the thermal properties of β-Ga2O3 play a critical role. The thermal conductivity of β-Ga2O3 is expected to be three-dimensionally (3D) anisotropic due to the monoclinic lattice structure. In this work, the 3D anisotropic thermal conductivity tensor of a (010)-oriented β-Ga2O3 single crystal was measured using a recently developed elliptical-beam time-domain thermoreflectance method. Thermal conductivity along any direction in the (010) plane as well as the one perpendicular to the (010) plane can be directly measured, from which the 3D directional distribution of the thermal conductivity can be derived. Our measured results suggest that at room temperature, the highest in-plane thermal conductivity is along a direction between [001] and [102], with a value of 13.3 ± 1.8 W m?1 K?1, and the lowest in-plane thermal conductivity is close to the [100] direction, with a value of 9.5 ± 1.8 W m?1 K?1. The through-plane thermal conductivity, which is along the [010] direction, has the highest value of 22.5 ± 2.5 W m?1 K?1 among all the directions. The temperature-dependent thermal conductivity of β-Ga2O3 was also measured and compared with a theoretical model calculation to understand the temperature dependence and the role of impurity scattering.
关键词： monoclinic lattice,β-Ga2O3,anisotropic,time-domain thermoreflectance,thermal conductivity
更新于2025-09-04 15:30:14
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Deep level acceptors of Zn-Mg divalent ions dopants in β-Ga2O3 for the difficulty to p-type conductivity
摘要： β-Ga2O3 exhibits huge potential applications in next-generation power electronics with its wide band gap, large breakdown field and high Baligas’s figure of merit. The achievement of p-type conductive β-Ga2O3 faces hugely challenge due to the self-compensating process, while that is critically important to further extend its utility and applications. Although the acceptor deep levels of divalent ions dopants can explain the difficulty of p-type Ga2O3 theoretically, while the experimental evidence is lacked. Herein, Zn and Zn-Mg co-doped β-Ga2O3 thin films were prepared to investigate the acceptor levels of ZnGa and MgGa. The XPS results indicate that both Zn and Mg exhibit divalent ions when they replaced trivalent Ga ion. The doping concentration and band gap can modulate by solely changing the numbers of Zn and Mg pieces during the deposition process. The levels of ZnGa and MgGa are located at 0.79 eV and 1.00 eV respectively speculated by photoluminescence, such deep acceptor transition levels proved that it is difficult to obtain highly conductive p-type Ga2O3 by doping with divalent ions of Zn and Mg.
关键词： acceptor levels,p-type conductivity,photoluminescence,Zn-Mg doping,β-Ga2O3
更新于2025-09-04 15:30:14
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Faceting and metal-exchange catalysis in (010) β-Ga <sub/>2</sub> O <sub/>3</sub> thin films homoepitaxially grown by plasma-assisted molecular beam epitaxy
摘要： We here present an experimental study on (010)-oriented β-Ga2O3 thin films homoepitaxially grown by plasma assisted molecular beam epitaxy. We study the effect of substrate treatments (i.e., O-plasma and Ga-etching) and several deposition parameters (i.e., growth temperature and metal-to-oxygen flux ratio) on the resulting Ga2O3 surface morphology and growth rate. In situ and ex-situ characterizations identified the formation of (110) and (ˉ110)-facets on the nominally oriented (010) surface induced by the Ga-etching of the substrate and by several growth conditions, suggesting (110) to be a stable (yet unexplored) substrate orientation. Moreover, we demonstrate how metal-exchange catalysis enabled by an additional In-flux significantly increases the growth rate (>threefold increment) of monoclinic Ga2O3 at high growth temperatures, while maintaining a low surface roughness (rms < 0.5 nm) and preventing the incorporation of In into the deposited layer. This study gives important indications for obtaining device-quality thin films and opens up the possibility to enhance the growth rate in β-Ga2O3 homoepitaxy on different surfaces [e.g., (100) and (001)] via molecular beam epitaxy.
关键词： molecular beam epitaxy,metal-exchange catalysis,surface morphology,homoepitaxy,β-Ga2O3
更新于2025-09-04 15:30:14
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Measurement of ultrafast dynamics of photoexcited carriers in <i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub> by two-color optical pump-probe spectroscopy
摘要： We report results from ultrafast two-color optical pump-probe spectroscopy on bulk b-Ga2O3. A two-photon absorption scheme is used to photoexcite carriers with the pump pulse and free-carrier absorption of the probe pulse is used to record the subsequent dynamics of the photoexcited carriers. Our results are consistent with carrier recombination via defect-assisted processes. We also observe transient polarization-selective optical absorption of the probe pulse by defect states under nonequilibrium conditions. A rate equation model for electron and hole capture by defects is proposed and used to explain the data. Whereas the rate constants for electron capture by defects are found to be temperature-independent, they are measured to be strongly temperature-dependent for hole capture and point to a lattice deformation/relaxation process accompanying hole capture. Our results shed light on the mechanisms and rates associated with carrier capture by defects in b-Ga2O3.
关键词： two-color optical pump-probe spectroscopy,ultrafast dynamics,photoexcited carriers,carrier recombination,defect-assisted processes,β-Ga2O3
更新于2025-09-04 15:30:14