Investigation and fabrication of Cadmium Telluride (CdTe) single crystal as a photodetector

Abstract

Cadmium Telluride (CdTe) has a band gap of 1.5 eV at room temperature and is considered to be the most promising material for optoelectronic application. In the present work, we have selected the Bridgman grown CdTe single crystal and characterized it by Energy Dispersive Analysis of X-Rays (EDAX), Raman Spectroscopy, Photoluminescence Spectroscopy and Thermal Analysis techniques. EDAX has shown that there are no impurity elements present in CdTe sample and thereby proved its stoichiometry. We did Raman mapping up to the depth of 10 μm from the surface which has shown A1 mode at 121 cm−1 and TO mode at 140 cm−1. Raman spectra at low temperature from 80 K to 300 K is also studied on this sample. The photoluminescence spectra taken at room temperature with different excitation wavelength shows emission in different regions of the visible spectrum and IR region. TGA/DTA curves are recorded at three different heating rates from where we calculated various kinetic parameters. The I – V characteristics of prepared CdTe single crystal photodetector is measured at room temperature as well as low temperature up to 75 K. Pulse photoresponse at different biasing voltages at 50 mW/cm2 is recorded. Various parameters i.e. photocurrent, responsivity and detectivity from I – V characteristics has been determined. Photoconductivity measurements at different biasing voltage and at different polarizing angle is also carried out. The results obtained are explained in the paper in detail.