Thermal characterization of gallium oxide Schottky barrier diodes

A Review of β-Ga2O3 Power Diodes

As the most stable phase of gallium oxide, β-Ga2O3 can enable high-quality, large-size, low-cost, and controllably doped wafers by the melt method. It also features a bandgap of 4.7-4.9 eV, a critical electric field strength of 8 MV/cm, and a Baliga's figure of merit (BFOM) of up to 3444, which is 10 and 4 times higher than that of SiC and GaN, respectively, showing great potential for application in power devices. However, the lack of effective p-type Ga2O3 limits the development of bipolar devices. Most research has focused on unipolar devices, with breakthroughs in recent years. This review mainly summarizes the research progress fora different structures of β-Ga2O3 power diodes and gives a brief introduction to their thermal management and circuit applications.

β-Ga2O3-Based Power Devices: A Concise Review

Ga2O3 has gained intensive attention for the continuing myth of the electronics as a new-generation wide bandgap semiconductor, owing to its natural physical and chemical properties. In this review article, we selectively summarized the recent advances on the experimental and theoretical demonstration of β-Ga2O3-based power devices, including Schottky barrier diodes and field-effect transistors, aiming for an inherent comprehending of the operating mechanisms, discussion on the obstacles to be addressed, and providing some comprehensive guidance for further developments. In the short run, Ga2O3 may well be promising to lead power electronics.

Thermal Conductivity of β-Phase Ga2O3 and (AlxGa1-x)2O3 Heteroepitaxial Thin Films

Heteroepitaxy of β-phase gallium oxide (β-Ga₂O₃) thin films on foreign substrates shows promise for the development of next-generation deep ultraviolet solar blind photodetectors and power electronic devices. In this work, the influences of the film thickness and crystallinity on the thermal conductivity of (2̅01)-oriented β-Ga₂O₃ heteroepitaxial thin films were investigated. Unintentionally doped β-Ga₂O₃ thin films were grown on c-plane sapphire substrates with off-axis angles of 0° and 6° toward ⟨112̅0⟩ via metal-organic vapor phase epitaxy (MOVPE) and low-pressure chemical vapor deposition. The surface morphology and crystal quality of the β-Ga₂O₃ thin films were characterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The thermal conductivities of the β-Ga₂O₃ films were measured via time-domain thermoreflectance. The interface quality was studied using scanning transmission electron microscopy. The measured thermal conductivities of the submicron-thick β-Ga₂O₃ thin films were relatively low as compared to the intrinsic bulk value. The measured thin film thermal conductivities were compared with the Debye-Callaway model incorporating phononic parameters derived from first-principles calculations. The comparison suggests that the reduction in the thin film thermal conductivity can be partially attributed to the enhanced phonon-boundary scattering when the film thickness decreases. They were found to be a strong function of not only the layer thickness but also the film quality, resulting from growth on substrates with different offcut angles. Growth of β-Ga₂O₃ films on 6° offcut sapphire substrates was found to result in higher crystallinity and thermal conductivity than films grown on on-axis c-plane sapphire. However, the β-Ga₂O₃ films grown on 6° offcut sapphire exhibit a lower thermal boundary conductance at the β-Ga₂O₃/sapphire heterointerface. In addition, the thermal conductivity of MOVPE-grown (2̅01)-oriented β-(Al_xGa_1-x)₂O₃ thin films with Al compositions ranging from 2% to 43% was characterized. Because of phonon-alloy disorder scattering, the β-(Al_xGa_1-x)₂O₃ films exhibit lower thermal conductivities (2.8-4.7 W/m·K) than the β-Ga₂O₃ thin films. The dominance of the alloy disorder scattering in β-(Al_xGa_1-x)₂O₃ is further evidenced by the weak temperature dependence of the thermal conductivity. This work provides fundamental insight into the physical interactions that govern phonon transport within heteroepitaxially grown β-phase Ga₂O₃ and (Al_xGa_1-x)₂O₃ thin films and lays the groundwork for the thermal modeling and design of β-Ga₂O₃ electronic and optoelectronic devices.