Jiancheng Yang

Bio: Jiancheng Yang is an academic researcher from University of Florida. The author has contributed to research in topics: Schottky diode & Breakdown voltage. The author has an hindex of 19, co-authored 47 publications receiving 1858 citations.

A review of Ga2O3 materials, processing, and devices

Abstract: Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

High reverse breakdown voltage Schottky rectifiers without edge termination on Ga2O3

Abstract: Vertical geometry Ni/Au-β-Ga2O3 Schottky rectifiers were fabricated on Hydride Vapor Phase Epitaxy layers on conducting bulk substrates, and the rectifying forward and reverse current-voltage characteristics were measured at temperatures in the range of 25–100 °C. The reverse breakdown voltage (VBR) of these β-Ga2O3 rectifiers without edge termination was a function of the diode diameter, being in the range of 920–1016 V (average value from 25 diodes was 975 ± 40 V, with 10 of the diodes over 1 kV) for diameters of 105 μm and consistently 810 V (810 ± 3 V for 22 diodes) for a diameter of 210 μm. The Schottky barrier height decreased from 1.1 at 25 °C to 0.94 at 100 °C, while the ideality factor increased from 1.08 to 1.28 over the same range. The figure-of-merit (VBR2/Ron), where Ron is the on-state resistance (∼6.7 mΩ cm2), was approximately 154.07 MW·cm−2 for the 105 μm diameter diodes. The reverse recovery time was 26 ns for switching from +5 V to −5 V. These results represent another impressive advanc...

Radiation damage effects in Ga2O3 materials and devices

Abstract: The strong bonding in wide bandgap semiconductors gives them an intrinsic radiation hardness. Their suitability for space missions or military applications, where issues of radiation tolerance are critical, is widely known. Especially β-Ga2O3, an ultra-wide bandgap material, is attracting interest for power electronics and solar-blind ultraviolet detection. Beside its superior thermal and chemical stabilities, the effects of radiation damage on Ga2O3 are of fundamental interest in space-based and some terrestrial applications. We review the effect on the material properties and device characteristics of proton, electron, X-ray, gamma ray and neutron irradiation of β-Ga2O3 electronic and optoelectronic devices under conditions relevant to low earth orbit of satellites containing these types of devices.

High Breakdown Voltage (−201) $\beta $ -Ga2O3 Schottky Rectifiers

Abstract: $\beta $ -Ga2O3 Schottky barrier diodes were fabricated in a vertical geometry structure consisting of Ni/Au rectifying contacts without edge termination on Si-doped epitaxial layers ( $10~\mu \text{m}$ , $\text{n}\sim 4\times 10^{15}$ cm $^{-3})$ on Sn-doped bulk Ga2O3 substrates with full-area Ti/Au back Ohmic contacts The reverse breakdown voltage, ${V} _ \text {BR}$ , was a function of rectifying contact area, ranging from 1600 V at $31\times 10^{-6}$ cm2 (20- $\mu \text{m}$ diameter) to ~250 V at $22{\times }10^{-3}$ cm $^{-2}$ (053-mm diameter) The current density near breakdown was not strongly dependent on contact circumference but did scale with contact area, indicating that the bulk current contribution was dominant The lowest ON-state resistance, ${R} _\text {on}$ , was 16 $\text{m}\Omega \cdot $ cm2 for the largest diode and 25 $\text{m}\Omega \cdot $ cm2 for the 1600-V rectifier, leading to a Baliga figure-of-merit ( ${V} _\text {BR}^{2}/{R} _\text {on})$ for the latter of approximately 1024 MW $\cdot $ cm $^{-2}$ The ON-OFF ratio was measured at a forward voltage of 13 V and ranged from $3\times 10^{7}$ to $25\times 10^{6}$ for reverse biases from −5 to −40 V and showed only a small dependence on temperature in the range from 25 °C to 100 °C

A review of Ga2O3 materials, processing, and devices

Abstract: Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

Self-Powered Ultraviolet Photodetector with Superhigh Photoresponsivity (3.05 A/W) Based on the GaN/Sn:Ga2O3 pn Junction.

Abstract: Ultraviolet (UV) radiation has a variety of impacts including the health of humans, the production of crops, and the lifetime of buildings. Based on the photovoltaic effect, self-powered UV photode...

Perspective: Ga2O3 for ultra-high power rectifiers and MOSFETS

Abstract: Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping, and the availability of large diameter, relatively inexpensive substrates. These applications include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors, and advanced power management and control electronics. Wide bandgap (WBG) power devices offer potential savings in both energy and cost. However, converters powered by WBG devices require innovation at all levels, entailing changes to system design, circuit architecture, qualification metrics, and even market models. The performance of high voltage rectifiers and enhancement-mode metal-oxide field effect transistors benefits from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. Reverse breakdown voltages of over 2 kV for β-Ga2O3 have been reported, either with or without edge termination and over 3 kV for a lateral field-plated Ga2O3 Schottky diode on sapphire. The metal-oxide-semiconductor field-effect transistors fabricated on Ga2O3 to date have predominantly been depletion (d-mode) devices, with a few demonstrations of enhancement (e-mode) operation. While these results are promising, what are the limitations of this technology and what needs to occur for it to play a role alongside the more mature SiC and GaN power device technologies? The low thermal conductivity might be mitigated by transferring devices to another substrate or thinning down the substrate and using a heatsink as well as top-side heat extraction. We give a perspective on the materials’ properties and physics of transport, thermal conduction, doping capabilities, and device design that summarizes the current limitations and future areas of development. A key requirement is continued interest from military electronics development agencies. The history of the power electronics device field has shown that new technologies appear roughly every 10-12 years, with a cycle of performance evolution and optimization. The older technologies, however, survive long into the marketplace, for various reasons. Ga2O3 may supplement SiC and GaN, but is not expected to replace them.