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The aim of the present work is to prepare, test and analyze the electrical and optical characteristics of the p-
NiO/n-Si and n-ZnO/p-Si heterojunctions as building blocks in semiconductor devices. p-NiO thin films of 75 nm have
been prepared by thermal oxidation of Ni metallic films of 50 nm deposited by e-beam high vacuum evaporation
technique on n type silicon wafer with 30 Ω cm resistivity. The oxidation processes of nickel samples are performed at
430oC for 60 min in a controlled ambient of oxygen and argon maintaining the oxygen concentration of 70%. The structural characteristics observed by X - ray diffraction method showed a polycrystalline structure with strong peaks corresponding to cubic NiO. p-NiO / (n/n+) Si heterojunctions I-V characteristics revealed that p-type NiO thin films have been obtained and a value of ~2.2 V for forward threshold voltage. n-ZnO thin layers of about 200 nm thickness, doped with aluminum on 30 Ωcm resistivity p type silicon epitaxial wafers were obtained by spin coating, layer by layer, using zinc acetate (Zn(CH3COO)2⋅2H2O) and aluminum nitrate (Al(NO3)3⋅9H2O) with Al/ Al+Zn ratio in range 0.5 - 1.5 % followed by thermal treatment at 475 °C for 15 minutes. The obtained thin layers have a high transparency T>85% for NiO and >70 % for ZnO:Al) over a large spectral range and a low resistivity, ρ~10-4 Ωcm. The I-V characteristics of p-NiO/n– Si shows that this heterojunction has rectifying properties with turn on voltage in the range 1.5- 2V and reverse breakdown voltage >10 V. By fitting the forward voltage we have obtained for p-NiO/n-Si a series resistance id RS=16 kΩ, an ideality factor of >10 and a barrier height of 0.648 eV. The optical response of n-ZnO/p- Si heterojunction was investigated at λp = 475 nm and the measured values of the photocurrent about 10 μA confirms the possibility to use them as ultraviolet radiation detectors.
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