Exploration of doping-dependent structural, optical, and electrical properties of thermally evaporated CdSe thin films for improved photodetection performance

Abstract

This paper is devoted to studying the influence of indium doping on the structure, morphology, and electrical properties of thermally deposited CdSe thin films as a powerful approach toward optimized photodetection performance. The variation of incorporated In-level modulated crystallographic and surface morphology as obtained from the X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Besides, the optical properties of the prepared In:CdSe thin films were investigated spectrophotometrically in the UV-Vis-NIR regions. We have deeply evaluated not only the dispersion and absorption features but also the opto-(electronic) parameters of the prepared films. The spectral nonlinear optical refractive index, absorption coefficient, and susceptibility were estimated and analyzed. The tunability of the structural and optical properties is introduced in a systematic explainable manner in terms of the recorded elemental analysis using EDX. The dark conductivity measurements of the prepared films declared that doped CdSe film of 37.5 wt% indium achieved the highest electrical conductivity which coincident with all the structural and optical characterization findings. Furthermore, the fabricated In:CdSe films were integrated with p-type silicon for Au/In:CdSe/p-Si/Al heterojunction formation. The electrical and microelectronic parameters of the designed junctions have been assessed using the measured current-voltage relations. The charge carriers' conduction mechanism within the constructed junctions has been explained in detail. Eventually, the photodetection performance of the fabricated heterojunctions has been tested using the recorded (I-V) and (I-t) response curves. Evidently, 37.5 wt% In doping concentration in the CdSe structure achieved superior optical and electrical properties which have been reflected in its promising photodetection performance compared to not only the other pure and doped films in the present study but also other prior reports. Such a device achieved Jphoto, Rλ, EQE, D*, and tr/tf of about 34.4 mA/cm2, 3.43 A/W, 800%, 4.6 × 1010 Jones, and 3.06 ms/6.10 ms, respectively.