Nanostructured surfaces

Formation of ZnO/Si isotype heterojunction at room temperature
O.S. Oberemok1, T.M. Sabov, O.V. Dubikovskyi, O.V. Kosulya,V.P. Melnik, V.P. Kladko, B.M. Romanyuk, V.G. Popov
1 Department of Ion Beam Engineering, V.Lashkaryov Institute of Semiconductor Physics of the NAS of Ukraine. Prospect Nauki, 41, Kyiv-03028, Ukraine. 
E-mail: ober@isp.kiev.com

ZnO/n-Si thin film isotype heterojunctions are promising structures for the creation of high-speed diode detectors of ultraviolet radiation. The epitaxial growth of ZnO film on the silicon substrate is complicated by the big mismatch of lattices between ZnO and Si (up to 15.4%). The main problem that arises in the ZnO/Si heterostructure formation is the defect generation in the ZnO film and at the ZnO/Si interface. It leads to uncontrolled processes of generation and recombination of charge carriers in the space charge region. 
The initial stages of film growth were studied to determine the deposition conditions for the formation of a heterojunction with diode characteristics at room temperature. 

ZnO films were deposited on the n-Si (100) surfaces by magnetron sputtering of ZnO target at room temperature. The crystalline structure, roughness and relief of the surface and the ZnO/Si interface were investigated. It is shown that the ZnO film growth occurs in the form of columns with the same orientation. At the increasing of film thickness to 67 nm, I-V characteristics already show the formation of a diode structure with a nonideality factor of ≈ 2.7. The value of the built‐in voltage is the intersection of the (1/C2) versus V and was found to be 0.66 V at the 1 MHz frequency. Thus, the regimes of diode structure were investigated.