【Domestic Papers】Enhanced linear dynamic range and response speed in interdigital-electrode solar-blind photodetector by contact engineering

      Researchers from the Hubei University have published a dissertation titled "Enhanced linear dynamic range and response speed in interdigital-electrode solar-blind photodetector by contact engineering" in Applied Physics Reviews.

Project Support

      This work was supported by the Major Program of Hubei Province under Grant No. 2023BAA009, the National Natural Science Foundation of China (Grant No. 22105162), and the Natural Science Foundation of Hubei Province (Grant No. 2023AFB623).

Background

      Solar-blind ultraviolet (SBUV) photodetectors play an important role in military and civilian fields such as environmental monitoring, missile tracking, flame alarm, security communication, and oil pollution detection. As an ultra-wide bandgap (UWBG) semiconductor (Eg~4.9 eV), Ga₂O₃ has been used to make a variety of electronic devices, including ultraviolet detectors, field-effect transistors, Schottky diodes, and power devices. In addition, Ga₂O₃ has a high absorption coefficient for SBUV light, high environmental stability, high breakdown electric field strength (7–8MV/cm), and low cost. Among them, β-Ga₂O₃ is the most stable phase, and the other phases are metastable phases, which can be converted into b phases under certain conditions. The large-scale preparation of high quality thin films is the basis for the commercialization of Ga₂O₃. In recent years, much work has been done on the growth of Ga₂O₃ films, such as chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), magnetron sputtering and molecular beam epitaxy (MBE). Among these methods, MOCVD is the preferred method for industrialization, which can achieve wafer-scale single-crystal quality of β-Ga₂O₃ films.

Abstract

      As an ultra-wide bandgap semiconductor, gallium oxide (Ga₂O₃) has great market potential in the field of solar-blind UV photodetectors. However, the slow response time of hundreds of milliseconds has seriously hindered the commercialization of the Ga₂O₃ photodetector. Here, we design an interdigital-electrode solar-blind UV β-Ga₂O₃ photodetector by using high-work function metal Pd as contacts. The atomic transmission electron microscopy data reveal that the Pd-Ga₂O₃ interface is clean and smooth, composed of a Ga₂O₃ single crystal and a local Pd single crystal, beneficial for weakening Fermi-level pinning. A low-damage and low-defect contact interface provides an excellent photoelectric response time of 2.4 ms (rise)/2.6 ms (descend) and a large linear dynamic range of 140 dB. On a 2-in. wafer of β-Ga₂O₃ film, we made a 12 × 12 array in which all 64 (8 × 8) devices tested maintained consistent performance and high reliability. Our high-performance Pd-Ga₂O₃ interdigital-electrode solar-blind photodetectors provide assurance for UV communication and imaging applications.

Conclusion

      The solar-blind UV photodetectors show ultra-clean interfaces based on β-Ga₂O₃ single-crystal films and Pd interdigital electrodes. Under the 255 nm DUV light, the Pd-Ga₂O₃ photodetector shows the detectivity of 6.16×10¹⁴ Jones, the responsivity of 186A/W, the on/ off ratio of 10⁵ , the response times of τ_r= 2.4 ms, τ_d= 2.6 ms, and the linear dynamic range of 140 dB. Our high-performance Pd-Ga₂O₃ interdigital-electrode photodetectors provide assurance for UV communication and imaging applications.