LAUSR

In this paper, we report a method of increasing the sensitivity of a silicon near-infrared sensor. The sensor is realized by forming multiple trench-type photodiodes in a silicon chip. The trench photodiodes can be formed using conventional semiconductor fabrication equipment. The device structure allows the depletion layer to be spread over the entire sensor chip even at a bias voltage of 10 V or less. The sensor chip can thereby extend the collection area of photoelectrons to the maximum. At a chip thickness of 540 $\mu \text{m}$ , the conversion efficiency for near-infrared wavelengths between 940 and 1020 nm is more than 80% at room temperature. In addition, the electrical characteristics and response performance of the fabricated 2.4 mm $\times2.4$ mm test chips are reported. Since the proposed method can achieve a high conversion efficiency at low voltage without cooling in silicon semiconductors, it is expected to provide a low-cost and compact solution for various near-infrared receiver devices such as these for Internet of Things (IoT) applications.