Wide bandgap (WBG) and ultra-WBG (UWBG) semiconductor devices exhibit superior performance with higher breakdown voltage and lower ON-resistance compared to Si-based devices, rendering them highly competitive in the field of electric energy conversion and communication. Especially, GaN, as one of the representative materials in WBG semiconductors, has progressed to the stage of industrial realization, and the new generation of UWBG semiconductors such as Ga₂O₃ has become a popular research focus in the last decade for power electronics applications. However, the primary challenge faced by these advanced semiconductor devices is thermal management, particularly in high-power application, which leads to a serious degradation in electrical performance and long-term reliability. Therefore, there is an urgent need for effective thermal management technologies. This review comprehensively summarizes recent advances in device-level thermal management techniques for WBG and UWBG semiconductors, ranging from internal device structure optimization to a series of external strategies for enhancing thermal diffusion. These strategies include enhancing the internal thermal dissipation through device architecture optimization, substrate thinning, high thermal conductivity substrate bonding and coverage, flip chip package, active method of microchannel cooling, and transient thermal management techniques. Finally, we discuss the existing technical challenges, potential solutions, and further development opportunities in thermal management techniques, with the aim of addressing the critical thermal dissipation issue to facilitate the further industrialization of WBG and UWBG semiconductors.

In this Letter, a vertical β-Ga2O3 Schottky barrier diode (SBD) featuring a composite termination structure with dual-layer field plate and self-aligned etched mesa (DFPM-SBD) is proposed. By combining a high-k HfO2 and SiO2 bilayer dielectric as the field plate termination, the interfacial trap state can be effectively reduced and the electric field crowding effect can be effectively alleviated in β-Ga2O3 SBD. Moreover, the self-aligned etching process is implemented using high-hardness Pt metal as the etching mask, effectively eliminating alignment deviation, thereby contributing to a high breakdown voltage (BV). The experimental result demonstrates that the DFPM-SBD achieves a low Von of 0.68 V (@1 A/cm2), an ideality factor (η) of 1.07, a Schottky barrier height (qΦb) of 1.25 eV, a low specific on-resistance of 3.85 mΩ cm2 along with a high BV of 2050 V, yielding a Baliga's power figure of merit of 1.1 GW/cm2. Furthermore, the interface trap density (Dit) of β-Ga2O3 SBDs is measured, and it is found that the HfO2 layer can effectively reduce the interfacial Dit from 3.25 × 1012 to 4.76 × 1011 cm−2eV−1, showing an 85% reduction, with a trap energy level located at ET in a range of 0.21–0.25 eV below the EC and the time constant ranging from 4.46 to 8.36 × 10−5 ms. Therefore, this work provides important guidance of β-Ga2O3 SBD for high-power applications, pushing the development of ultra-wide gap semiconductors greatly.

In this paper, it is demonstrated that the AlGaN high electron mobility transistor (HEMT) based on silicon wafer exhibits excellent high-temperature performance. First, the output characteristics show that the ratio of on-resistance (R_ON) only reaches 1.55 when the working temperature increases from 25 °C to 150 °C. This increase in R_ON is caused by a reduction in optical phonon scattering-limited mobility (μ_OP) in the AlGaN material. Moreover, the device also displays great high-performance stability in that the variation of the threshold voltage (ΔV_TH) is only 0.1 V, and the off-state leakage current (I_D,off-state) is simply increased from 2.87 × 10⁻⁵ to 1.85 × 10⁻⁴ mA/mm, under the operating temperature variation from 25 °C to 200 °C. It is found that the two trap states are induced at high temperatures, and the trap state densities (D_T) of 4.09 × 10¹²~5.95 × 10¹² and 7.58 × 10¹²~1.53 × 10¹³ cm⁻² eV⁻¹ are located at E_T in a range of 0.46~0.48 eV and 0.57~0.61 eV, respectively, which lead to the slight performance degeneration of AlGaN HEMT. Therefore, this work provides experimental and theoretical evidence of AlGaN HEMT for high-temperature applications, pushing the development of ultra-wide gap semiconductors greatly.

In this letter, an E-Mode GaN-Si(100) monolithic heterogeneous integration cascode switch (RBMHIC-switch) with reverse blocking compatibility on a SiC substrate with an AlN buffer layer is demonstrated. The RBMHIC-switch with L_GD of 22 μm showed a threshold voltage (V_TH) of 2.64 V, a large forward gate voltage swing of 16.27 V, a turn-on voltage (V_ON) of 0.3 V, and an extremely low reverse leakage current (IR) of 3.5 × 10-4 mA/mm at -2000 V. The forward breakdown voltage (V_FBR) of 2264 V and reverse breakdown voltage (V_RBR) of 2183 V with a specific on-resistance (R_{ON, SP}) of 3.74 mΩ·cm² were achieved, resulting in a forward power figure of merit (PFOM = V_BR²/R_{ON, SP}) of 1.35 GW/cm² and reverse PFOM of 1.27 GW/cm². The ratio between dynamic-R_ON and static-R_ON was 1.104 and 1.127 after a 10 ms 1900 V drain stress voltage (V_DS-OFF) and a 10 ms -1900 V V_DS-OFF (delay time = 1 μs) for the RBMHIC-switches, respectively, which were the best among all existing GaN power devices with reverse blocking capability. The thermal resistance at different temperatures was also extracted. The RBMHIC-switche shows decent overall characteristics as compared to the reported results.

Gallium nitride (GaN) is a high-performance wide bandgap semiconductor material with unique physical and chemical properties such as higher breakdown electric field, higher electron density, superior electron mobility and saturation velocity. These properties endow GaN with unparalleled advantages in high-frequency and high-power applications. However, a primary challenge faced by the industrialized GaN HEMT is thermal management, particularly in handling higher power densities, which leads to a serious degradation in electrical performance and long-term reliability. In this study, electrothermal analysis for GaN HEMT is conducted based on two thermal resistance models for natural air cooling and microchannel cooling, proving a minimum 40% reduction in Rj-a using microchannel cooling and an optimal coolant flow rate to guide the actual experiment. Furthermore, the experimental result shows that microchannel cooling technology significantly enhances the thermal convection capacity, resulting in a 35.2% increase in the saturation current. Moreover, the Rj-a can be reduced to 13.5 K/W with 65% improvement at a cooling flow rate of 460 mL/min, and the surface heat flux density reaches 2200 W/cm2, which is 106% higher than that of natural air cooling.