Ultrawide bandgap β-gallium oxide (β-Ga2O3) is emerging as a viable candidate for next-generation high-power electronics, including Schottky barrier diodes (SBDs) and field-effect transistors (FETs). This is due to its excellent material properties such as ultrawide bandgap of 4.6–4.9 eV, high breakdown electric field of 8 MV/cm, very high Baliga’s figure of merit (BFOM) and mature technology for large bulk single crystals, and epitaxial techniques with controllable n-type doping. Ohmic and rectifying metal–semiconductor contacts on β-Ga2O3 have been developed over the past decade. This work comprehensively reviews the recent development of metal–semiconductor contacts on β-Ga2O3. We start with basic concepts of metal–semiconductor contacts, which is followed by summarizing the current literature on ohmic and Schottky contacts on β-Ga2O3. Finally, the status of high-power Schottky diode contact on β-Ga2O3 is presented.

Temperature dependent current transport mechanism in Ni/β-Ga2O3 Schottky Barrier Diodes was studied using current-voltage (I-V) and capacitance-voltage (C-V) characterization techniques in the range of 78–350 K. Schottky barrier height ϕ b0 and ideality factor ɳ from I-V characteristics were found to be 1.27 eV and 1.12, respectively, at room temperature. Plots of barrier height and ideality factor with inverse of temperature show strong temperature dependency and a deviation from barrier height obtained from C-V characteristics. The temperature dependence of barrier height and ideality factor assigned to barrier inhomogeneity at Ni/β-Ga2O3 interface, and modulated by the potential fluctuation model. Diode turn-on voltage and turn-on resistance at 300 K were found to be 1.08 eV and 7.80 mΩ-cm2, respectively. A large rectification ratio of the order of 1012 was obtained at room temperature and also the rectification ratio of the order of 109 was consistent over the whole temperature range (78–350 K).

Mixed-dimensional heterostructures are emerging to be very promising for the future electronic and optoelectronic applications. Here, we report on the fabrication and characterization of a 2D/3D vertical van der Waals p-n heterojunction based on p-type gallium selenide (GaSe) and n-type gallium oxide (Ga2O3). Kelvin Probe Force Microscopic (KPFM) measurements have been conducted to estimate the difference in the surface potential values between GaSe and Ga2O3, which is further used to find out the conduction band offset value at the GaSe/Ga2O3 hetero-interface to design the band diagrams. The current-voltage measurements on the device display a diode-like behavior which is attributed to the type-II band alignment, present at the p-n junction interface as per the electron affinities and bandgap values of GaSe and Ga2O3. The device exhibits a high current rectification ratio of ~2500 extracted at ± 5 V. The photoresponse properties of the heterostructure are also studied and the figure of merit parameters of the photodetector such as photoresponsivity and specific detectivity have been evaluated for the fabricated device. Since the GaSe/Ga2O3 heterojunction holds a great potential in the field of efficient optoelectronic devices, we believe our study could pave the way to designing innovative optoelectronic devices by integrating low-dimensional materials with conventional 3D semiconducting materials.

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In this article, we report on high-performance deep ultraviolet photodetectors (DUV PDs) fabricated on metal−organic chemical vapor deposition (MOCVD)-grown β-Ga 2 O 3 heteroepitaxy that exhibit stable operation up to 125 °C. The fabricated DUV PDs exhibit self-powered behavior with an ultralow dark current of 1.75 fA and a very high photo-todark-current ratio (PDCR) of the order of 10 5 at zero bias and >10 5 at higher biases of 5 and 10 V, which remains almost constant up to 125 °C. The high responsivity of 6.62 A/W is obtained at 10 V at room temperature (RT) under the weak illumination of 42.86 μW/cm 2 of 260 nm wavelength. The detector shows very low noise equivalent power (NEP) of 5.74 × 10 −14 and 1.03 × 10 −16 W/Hz 1/2 and ultrahigh detectivity of 5.51 × 10 11 and 3.10 × 10 14 Jones at 0 and 5 V, respectively, which shows its high detection sensitivity. The RT UV−visible (260:500 nm) rejection ratios of the order of 10 3 at zero bias and 10 5 at 5 V are obtained. These results demonstrate the potential of Ga 2 O 3 -based DUV PDs for solar-blind detection applications that require high-temperature robustness.