A high-performance solar-blind photodetector based on Cr-doped gallium oxide (Ga ₂ O ₃ ) has been fabricated. A 140-nm-thick Ga ₂ O ₃ layer was mechanically exfoliated from bulk crystal. The photodetector was based on a field-effect transistor structure, which showed a very high photo-to-dark current ratio larger than 10 ⁶ and excellent current saturation. When the photodetector was tested with a 254-nm ultra-violet light, the ratio of drain current with and without the UV light reached nearly six orders of magnitude. The dark current was as low as 5 pA. Furthermore, the current rise time and decay time were both about 25 ms. High responsivity of ${4.79} \times {10}^{{5}}$ A/W and external quantum efficiency of ${2.34} \times {10}^{{6}}$ also have been achieved at the same time.

A high-performance Schottky diode based on a 600-μm-thick Cr-doped β-Ga2O3 single crystal has been fabricated using SnOx as the Schottky contact. The SnOx film was deposited in argon/oxygen mixture gas to ensure an oxygen-rich stoichiometry in Ga2O3 near the Schottky interface, thus reducing oxygen deficiency related interface state density. The SnOx film included three components: Sn, SnO, and SnO2, as revealed by X-ray photoelectron spectroscopy characterization. The high quality Ga2O3 single crystal grown by an edge-defined film-fed method has a carrier concentration of 1.0 × 1018 cm-3 and an electron mobility of ~90 cm2/Vs. Current density-voltage characteristics of the Schottky diode demonstrated high performance with a large barrier height of 1.19 eV, a close-to-unity ideality factor of 1.02, and a high rectification ratio beyond 1010. Frequency-dependent capacitance and conductance analysis revealed that the maximum active interface state density is 2.46 × 1012 eV-1cm-2 at a frequency of 500 kHz.

High-performance flexible InGaZnO-based Schottky diodes are fabricated on polyethylene terephthalate (PET) and polyimide (PI) substrates at room temperature without any thermal treatment. The diode performance improves significantly by either oxygen plasma or UV-ozone treatment on Pd anode. X-ray photoelectron spectroscopy indicates that both treatments lead to Pd surface oxidation. The oxygen plasma treatment results in more complete oxidation, and thus ensures better oxygen stoichiometry at the Schottky interface and a higher anode work function. This leads to high performance with on/off ratios of 7.3 × 10 ⁶ and 2.6 × 10 ⁴ , barrier heights of 0.79 and 0.76 eV, and ideality factors of 1.22 and 1.19 on PET and PI, respectively. Interestingly, these flexible diodes show improved performance after storing in ambient air for two years, and fittings on the reverse currents indicate an improved barrier uniformity. The flexible diode on PET after a two-year storage achieves a high on/off ratio of 2 107, a large barrier height of 0.80 eV, a close to unity ideality factor of 1.09, a high breakdown voltage of -7.5 V, and robust performance upon outward or inward bending, which is, to the best of our knowledge, the highest performance in reported flexible diodes to date.

In recent years, because of stringent needs in the fabrication of silicon carbide (SiC) power devices, laser annealing has been introduced to achieve local ohmic contact. In this paper, the laser annealing research for the ohmic contact process of SiC power devices is reviewed, which is mainly divided into four aspects: laser process mechanism, ohmic contact electrode materials, and substrate materials. The effect of laser parameters on ohmic contact and the annealing process on SiC diode devices is also reviewed. Progress of other substrate materials, namely 6H-SiC and semi-insulating 4H-SiC-based devices with laser annealed ohmic contacts, is also briefly discussed, in which formation of semi-insulating SiC ohmic contacts is derived from laser irradiation at the interface to produce 3C-SiC. Some experiment results have been shown in the passage, such as XRD, SEM, TEM, etc. In the review, it points out that the direction of application and development of the laser annealing process for improving the ohmic contact of SiC power devices is highly encouraging.

Achieving high interface thermal conductance is one of the biggest challenges in the nanoscale heat transport of GaN-based devices such as light emitting diodes (LEDs), and high electron mobility transistors (HEMTs). In this work, we experimentally measured thermal boundary conductance (TBC) at interfaces between GaN and the substrates with AuSn alloy as a commonly-used adhesive layer by time-domain thermoreflectance (TDTR). We find that the TBCs of GaN/Ti/AuSn/Ti/Si, GaN/Ti/AuSn/Ti/SiC, and GaN/Ti/AuSn/Ti/diamond, are 16.5, 14.8, and 13.2 MW·m⁻²·K⁻¹ at room temperature, respectively. Our measured results show that the TBC of GaN/Ti/AuSn/Ti/SiC interface is inferior to the TBC of pristine GaN/SiC interface, due to the large mismatch of phonon modes between AuSn/Ti and substrates, shown as the difference of Debye temperature of two materials. Overall, we measured the TBC at interface between GaN and thermal conductive substrates, and provided a guideline for designing the interface between GaN and substrate at HEMT from a thermal management point of view.

A carving, cutting, and flip-chip bonding process is proposed for the fabrication of flexible electric double layer transistors (EDLTs) with low cost. Solution processed poly(styrenesulfonic acid sodium salt) is used as a gate dielectric. The large EDL-specific capacitance ( $4.5~\mu \text{F}$ /cm ² at 20 Hz) can induce very high charge carrier density in the InGaZnO (IGZO) channel layer, enabling the EDLTs to operate at a single-battery-drivable low voltage of 1.0 V with a high on-current of 10 ⁻⁴ A. The effect of IGZO layer thickness on the performance of EDLTs was investigated. The flexible EDLT with optimized IGZO thickness of 100 nm has achieved a high on/off ratio of $1.4 \times 10^{7}$ , a low threshold voltage of 0.51 V, a saturated field-effect mobility of 1.14 cm ² /Vs, and high positive gate bias stress stability. Furthermore, the achieved subthreshold swing, 76 mV/dec, is very close to the theoretical ideal minimum value.