ZnO homojunction core-shell nanorods ultraviolet photo-detecting diodes prepared by atomic layer deposition

We investigated the device properties of ZnO homojunction core-shell nanorods (NRs) ultraviolet (UV) photo-detecting diodes depending on fabrication process. ZnO homojunction core-shell NRs fabrication was realized by atomic layer deposition (ALD) of highly conformal ZnO shell with high concentration of nitrogen (HNZO) over hydrothermally synthesized n-ZnO NRs. ALD of HNZO was carried out using diethyl zinc (DEZ) and diluted ammonium hydroxide (NH4OH) as a Zn precursor and reactant/nitrogen source, respectively. On the electrical analysis, HNZO films is found to be weak n-type or ambiguous and, finally this HNZO attributed the rectifying property at the junction with n-type ZnO NRs. ZnO planar device was also fabricated as a comparative reference. Comparative study between core-shell and planar device has shown that the responsivity of the core-shell device was turned out to be about two times higher than that of planar device. Photoluminescence (PL) intensity of core-shell device was significantly reduced compared to that of planar device for overall region of wavelength, which was attributed to rapid separation of photo-generated carriers. The carrier transport mechanism in core-shell NR device is discussed based on band bending phenomenon.