39. Image Sensors

The advent of next-generation broadcasting systems such as 8K Super Hi-Vision has increased the demand for high-performance cameras. However, the low sensitivity of 8K cameras is challenging. To address this issue, we have developed the stacked complementary metal-oxide semiconductor (CMOS) image sensor overlaid with a gallium oxide (Ga₂O₃)/crystalline selenium (c-Se) photodiode. Using Ga₂O₃ decreased the dark current resulting from the injection of holes from the electrode. In addition, Ga₂O₃ doped with tin (Sn), which has higher carrier concentration, effectively reduced the operating voltage because the depletion layer spread into c-Se more easily as compared to that in non-doped Ga₂O₃. Furthermore, the crystallization of Ga₂O₃ improved the crystal orientation of the Se formed on β-Ga₂O₃, thereby decreasing the dark current.