【Domestic Papers】Long Shibing Team from University of Science and Technology of China | Ga₂O₃ photodetector based on alternating grid-voltage modulation

Research Introduction

      Recently, Long Shibing's research group at the University of Science and Technology of China proposed an alternating grid-voltage modulation scheme for Ga₂O₃ photodetector, which provides a new idea for the research of photodetector.Solar-blind photodetectors play an important role in today's photoelectric systems. However, almost all Solar-blind photodetectors based on photoconductivity effects are faced with the problem of response speed and speed dilemma (Short as “RS dilemma”), high responsivity leads to relatively long decay time. The trap center in the material prolongs the carrier lifetime, and the higher concentration of moving carriers under light is conducive to higher responsiveness, but the trap prolongs the trapping and de-trapping process of the trap center after the light disappears, resulting in high responsiveness of the device at the expense of response speed, which is the typical RS dilemma of photodetectors (FIG. 1a). The RS dilemma is particularly prominent in photodetectors based on Gallium Oxide, where there is an inherent trapping center that causes this phenomenon even in high-quality crystalline materials.

      In this work, a custom Alternating Gate Modulation (AGM) scheme was developed based on the amorphous Gallium Oxide (a-GaOx) thin-film Solar-blind photodetectors (FIG. 1b,c). Unlike traditional methods of controlling the photosensitive channel state through constant gate bias, the AGM scheme promotes high responsiveness and fast decay rate respectively through dynamic mode switching in a single detection cycle, thus overcoming the typical RS dilemma of photodetectors to some extent (FIG. 1d).

      In addition, with the above AGM regulation effect proved, a functional simulation of UV imaging of a 5×5 scale a-GaOx array was carried out, as shown in Figure 1e. Under four different operating conditions, namely Vgs=-10V, 0V, 10V and AGM modes, the same photoelectric detection task is performed and the image frame sequence is generated. Every 5 seconds, images (5 x 5 pixels) of the letters "U", "S", "T" and "C" are projected onto the array in sequence. Based on the comparison of all the image frames of each scheme, it can be seen that due to the synchronous enhancement of R and decay speed, the AGM can achieve the highest contrast without gaping due to the large dead zone, so the dynamic AGM scheme has good imaging application potential.

      The AGM scheme provides an opportunity for the photodetectors based on low-cost or low-quality materials to be among the high-performance devices, which is conducive to alleviating the harsh requirements of high-performance detectors on high-quality materials, so as to reduce the cost of industrialization.

Figure 1: (a)RS dilemma, (b,c)AGM biasing scheme, (d) improvement of response characteristics under AGM scheme, and (e) demonstration of imaging application

      The research results were published in Science China Information Sciences 2023, Volume 66, Issue 12 under the title "Breaking the responsivity-speeddilemma of a-GaOx photodetector by alternating gate modulation".  The first author of this paper is Zhang Zhongfang, PhD graduate of the University of Science and Technology of China (now postdoctoral fellow of Westlake University), corresponding author is Long Shibing, Professor and Zhao Xiaolong, Associate Researcher of the School of Microelectronics, the University of Science and Technology of China. The research was supported by a project from the National Natural Science Foundation of China and the Center for Micro and Nano Research and Manufacturing at USTC.