Enhanced photoresponse in Ag/CdTe/p-Si/Al heterostructure photodetectors, the influence of CdTe layer thickness

In this study, the influence of the sputtered CdTe interface layer thicknesses (0, 80, and 120 nm) in Ag/CdTe/p-Si/Al photodiodes (PDs) on the photoresponse of the samples to the halogen lamp illumination was investigated. The layers were characterized by FESEM, EDX, XRD, Raman, PL, Seebeck, UV–Vis. spectra, also I–V and I–t in the dark and under light illumination. We found: (1) while the thin CdTe interface layer is amorphous, the thick one has a polycrystalline cubic phase structure; (2) The insertion of the interface layer has led to an increase (about one order of magnitude) in the series resistance of the samples, leading to a decrease in the dark current (I_D) of their own devices; (3) The sample with the thickest CdTe layer has the highest active region volume and the highest light absorbance, leading to the highest photocurrent (I_P) and therefore the highest light sensitivity S (= I_P/I_D) of ~300, which is the highest value reported in CdTe/p-Si heterostructure PDs; (4) all the fabricated samples have fast response times (less than 200 ms).