Investigation of nc-PbS/a-Si1−xCx:H/pSi(1 0 0) heterostructures for LED applications

In order to study the possibility to develop a device which could be suitable for applications in optoelectronic such as light emitting diodes, heterostructure based on nc-PbS/a-SiC:H were investigated. The attention has been focused on the structural, optical and electrical properties of structures of the form Au/PbS/a-Si1−xCx:H/pSi(1 0 0)/Al as a function of the deposition temperature of the a-Si(1−x)Cx:H films. Those later were prepared by dc magnetron sputtering technique on p-type Si(1 0 0) by using 65 sprigs of silicon carbide (6H–SiC). The deposition temperatures of the a-SiC:H films were 150, 250 and 500 °C, respectively. Optical properties were investigated using UV–visible transmittance spectroscopy and photoluminescence. The optical response was studied in the wavelength region from 350 up to 1000 nm for different thicknesses of the amorphous films. The results reveal that optical gap (Eg) of a-Si1−xCx:H films obtained at 150 °C, 250 °C and 500 °C were 2.51 eV, 2.19 eV and 1.81 eV, respectively. The spectral response of Au/PbS/a-Si1−xCx:H/pSi(1 0 0)/Al structures with a-Si1−xCx:H film deposited at 250 °C, exhibits a maximum value at λ = 950 nm while for structure with a-Si1−xCx:H film obtained at 150 °C, the inverse phenomena was noticeable, a maximum value of λ was observed at 400 nm. By photoluminescence, blue emission from all the structures was observed at room temperature (RT) and a high emission was obtained for sample which amorphous film was deposited at 500 °C. We have used current–voltage characteristics to determine the Schottky barrier height (SBH) and ideality factor (n). An enhancement of the SBH was observed and the ideality factor was found to be near unity for structure which amorphous a-Si1−xCx:H film was obtained at 250 °C.

► Up to now, much effort has been devoted to preparation heterostructures with different method.
► Among these methods, CBD is a relatively facile and inexpensive method.
► In this study, in order to preparation heterostructures, CBD method has been used.
► In the past there has been no report on spectral response and PL properties of heterostructures of PbS/SiC/Si.
► The some properties of structure have been investigated with XRD, PL and I–V Characteristics.