Nano-structured Cu(In,Al)Se₂ near-infrared photodetectors

We have demonstrated nano-structured Cu(In,Al)Se₂ (CIAS) near-infrared (NIR) photodetectors (PDs). The CIAS NIR PDs were fabricated on ZnO nanowires (NWs)/ZnO/Mo/ITO (indium tin oxide) glass substrate. CIAS film acted as a sensing layer and sparse ZnSe NWs, which were converted from ZnO NWs after selenization process, were embedded in the CIAS film to improve the amplification performance of the NIR PDs. X-ray diffraction patterns show that the CIAS film is a single phased polycrystalline film. Scanning electron microscopy was used to examine the morphology of the CIAS film and the growth of NWs. Two detection schemes, plain Al-CIAS-Al metal-semiconductor-metal structure and vertical structure with CIAS/ZnSe NWs annular p-n junctions, were studied. The nano-structured NIR PDs demonstrate two orders of magnitude for the annular p-n junction and one order of magnitude for the MSM structure in photocurrent amplification. The responsivities of the PDs using both sensing structures have the same cut-off frequency near 790 nm.