Optoelectronic Properties of CdSe/Si Heterojunction
Waseem Najeeb Ibrahim

In this paper n-CdSe/p-Si heteroj unction photodetector was fabricated by thermal-evaporation technique of CdSe thin film grown onto single crystalline Si substrate . The energy gap of CdSe film was estimated from transmittance spectra and found to be (1.89 eV) . The temperature dependence of Seebeck coefficient was studied . The conductivity of CdSe thin film is n-type and the value of activation energy is (0.59 eV). Heterojunction properties included dark and illuminated current-voltage (I-V) and capacitance-voltage (C-V) characteristics. From I-V plot, junction ideality factor for heterojunction was calculated to be 1.43, and providing information about the current transport mechanism. The linear variation of the experimental curve C-2 vs. V is indicative of the presence of abrupt heterojunction and it used to determine the experimental value of built-injunction potential Vbi . From illuminated I-V plot at different intensity levels (90,180,240) mW/cm2 , the linearity behavior of CdSe/Si heterojunction was investigated .
Keywords: CdSe thin film; Si; Heterojunction; Thermal evaporation; Energy band gap; Seebeck coefficient; I-Vcharacteristics; C-Vmeasurements.