【Domestic Papers】Songshan Lake Materials Laboratory——Probing interfacial states in β-Ga₂O₃/SiO₂ TFTs for high-response broad-band photodetection

      Researchers from the Songshan Lake Materials Laboratory have published a dissertation titled "Probing interfacial states in β-Ga₂O₃/SiO₂ TFTs for high-response broad-band photodetection" in Applied Physics Letters.

Researchers Introduction

      Located in Dongguan, one of the main cities in the Guangdong-Hong Kong-Macao Greater Bay Area, Songshan Lake Materials Laboratory (SLAB) started construction on December 22, 2017 and completed registration in April, 2018. As one of the first Guangdong provincial laboratories, SLAB consists of four core sections: the Frontier Research Center, the Public Technology Platform and Large-scale Scientific Facilities, the Model Factory for Innovation, and the South Bay Interdisciplinary Science Center, which will form the entire chain of "frontier basic research → applied basic research → industrial technology research → industrial transformation". It is expected to become an internationally recognized southern base for new materials research and development, an important component of China’s materials research, and a new window of interdisciplinary cooperation in the Guangdong-Hong Kong-Macao Greater Bay Area.

Program Support

      This work was supported by the National Natural Science Foundation of China (Grant Nos. 12174275, 62174113, and 62204169), Youth Innovation Team of colleges and universities in Shandong Province (Grant No. 2022KJ223), and Shandong Provincial Natural Science Foundation (Grant No. ZR2021QF020)

Abstract

      Mechanically exfoliated β-Ga₂O₃ flakes preserve bulk material's single crystallinity for easy integration but suffer from interfacial defects that greatly influence device performance. In this paper, we report a quantitative characterization of interfacial states in phrase β-Ga₂O₃/SiO₂ thin-film transistors and then propose their beneficial application in achieving high-response broad-band photodetection. Photo-excited charge collection spectroscopy technique was employed to probe the interfacial states, revealing a substantial density (∼4 × 10¹² cm⁻² eV⁻¹) of deep-level states ranging from 2.5 to 3.7 eV below the conduction band. Intriguingly, a photoresponsivity as high as 2 × 10⁴ A/W was achieved via utilizing these interfacial states, along with the tunable broad-band response ranging from 335 to 496 nm. This research enhances both the well-industrialized silicon devices and the emerging β-Ga₂O₃ technologies. Furthermore, it introduces a profound concept: defects, once seen as flaws, can be assets when their characteristics are thoroughly understood.

Summary

      In summary, the interfacial traps in the β-Ga₂O₃/SiO₂ TFT, together with their utilization in high-response broad-band photodetection, are comprehensively investigated in this paper. An intriguing phenomenon emerged in single-crystal β-Ga₂O₃/SiO₂ TFTs upon illumination of these TFTs with photons of energies lower than the bandgap. Specifically, a continuous decrease in V_ON and an anomalous PPC effect during photoresponse tests were attributed to the interfacial traps. These traps were probed using the PECCS-IV technique, revealing discrete trap levels spanning from (CBM-2.5eV) to (CBM-3.7eV), with an areal density approximating 4 × 10¹²cm^-2. These deep interfacial traps were leveraged advantageously in designing V_GS and illumination of mutually modulated phototransistors, achieving high-response (R=2 × 10⁴ A/W), broad-band (335–496nm) photodetection. This paper aims to provide valuable insights not only for the established field of silicon devices and the rapidly evolving β-Ga₂O₃ devices but also for a wide range of electronic devices that may be plagued by similar defects.

Graphic Abstract