High-Performance Silicon-Compatible Large-Area UV-to-Visible Broadband Photodetector Based on Integrated Lattice-Matched Type II Se/n-Si Heterojunctions.

A gold-induced NH4Cl-assisted vapor-based route is proposed and developed to achieve vertically aligned submicron Se crystals on lattice-matched (111)-oriented silicon substrates, based on which a high-performance large-area silicon-compatible photodetector is constructed. Thanks to the energy band structure and the strongly asymmetrical depletion region, the fabricated Se/Si device maintains a similar wavelength cutoff to that of selenium devices before the IR region, along with a high-performance broadband photoresponse in the UV-to-visible region. The large-area photodetector maintains a very low leakage current under a -2 V bias, and a high on/off ratio of 103-104 is obtained with a high photocurrent of 62 nA at 500 nm. A photoresponse is clearly observed when the bias voltage is removed. The pulse response precisely provides a high response speed (τrise + τfall ≈ 1.975 ms), exceeding the fastest Se-based photodetectors in current reports. The enhanced photoelectric properties and the self-power photoresponse mainly derive from the integrated high-quality Se/n-Si p-n heterojunctions with both lattice match and type II energy band match.