Fabrication and Characterization of n-ZnS/p-Si and n-ZnS:Al/p-Si Heterojunction
Eman M. Nasir
Eman M. Nasir, Physics Department, University of Baghdad, College of Science, Baghdad University, Baghdad, Iraq.
Manuscript received on November 27, 2013. | Revised Manuscript received on December 13, 2013. | Manuscript published on December 30, 2013. | PP: 425-429 | Volume-3, Issue-2, December 2013. | Retrieval Number:  B2507123213/2013©BEIESP

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Abstract: A thin films of ZnS and ZnS:Al with various Al concentration (0, 1, 2)%wt has been prepared successfully. Also n-ZnS,p-Si and n-ZnS:Al, p-Si heterojunction detector(HJs) has been fabricated by thermal evaporation at different Al concentration. Structure of these films was characterized by X ray diffraction. The structures of these films are cubic zinc along (111) plane The reverse bias capacitance was measured as a function of bias voltage, and it is indicated that these HJs are abrupt. The capacitance decreases with increasing the reverse bias, and fixed at high value of reverse bias voltage. The capacitance increases with increasing Al concentration. The width of depletion layers decreases with increases Al concentration. The value of highest built in potential varies between (2-1.37V). The current-voltage characteristic of nZnS,p-Si and n-Zn S:Al,p-Si heterojunction show that the forward current at dark condition varies approximately exponentially with applied voltage and the junction was coincide with recombination-tunneling model, and reverse current exhibited a soft breakdown. The difference between forward and reverse current with applied voltage indicates that the detector has a high rectification characteristic. The value of ideality factor was varies between 2.58-3.22, and the value of tunneling constant (At) varies between 4.92-8.05V-1 . From the I-V measurements under illumination, the photocurrent increased with increasing Al concentration. The energy band diagram for HJ has been constructed.
Keywords: C-V measurements, Heterojunction, Vacuum evaporation, Zinc sulfide.