The dependence of optoelectric performance on channel length in photodetectors with MBE CdTe single-crystalline thin films on perovskite SrTiO₃

Photodetectors with molecular beam epitaxial CdTe single-crystalline films on SrTiO₃ were fabricated by varying the channel length to optimize the response performance. Optoelectric properties were characterized by semiconductor characterization system and high-speed oscilloscope. Crucial detecting parameters were extracted and their dependences on channel length were summarized. The responsivity, detectivity and gain increased exponentially with contracting the channel length while the response time and photo-to-dark current ratio exhibited a linear dependence. Ultrafast response speed with the ultrashort response time of ≈1.7 ms and high on/off ratio of ≈7.3 were achieved in the 3 μm channel size photodetector. Pole figure of CdTe/SrTiO₃ epitaxial system was performed to explain the low response properties and the trade-off among these response parameters was also discussed.