Synthesis of Al-doped CdS/Si nanoheterojunction arrays and their electrical and electroluminescence properties

The Al-doped CdS/Si nanoheterostructures were prepared by growing Al-doped CdS films on silicon nanoporous pillar array (Si-NPA) through chemical bath deposition (CBD). Their structure, electrical, and electroluminescence properties were investigated as a function of [Al]/[Cd]. At low [Al]/[Cd], Al ions tend to enter the lattice substitutionally, decreasing the lattice constants, micro-strain along (0 0 2) plane, and resistivity, and enhancing average crystallite size and carrier mobility. However, this behavior is reversed at high [Al]/[Cd], because Al ions tend to enter the lattice interstitially. The electroluminescence (EL) properties were most affected by Al doping. As Al concentration increases, the EL intensity initially increased rapidly to a maximum with [Al]/[Cd] and then decreased with further increased [Al]/[Cd]. The maximum of EL intensity was observed in sample S-0.07. Its EL intensity is 320 times that of S-0 and its applied voltages are very low. It could be observed by the naked eyes even at 3 V. These results indicated that Al-doped CdS/Si-NPA might be a great potential in constructing optoelectronic nanodevices. The measured results show the incorporation of suitable amount of Al would improve significantly the performances of CdS/Si-NPA heterojunctions, increasing the uniformity of CdS thin film, decreasing the resistivity, enhancing carrier mobility, improving obviously the rectification behavior, and increasing greatly the EL emission intensity. These results indicated that Al-doped CdS/Si-NPA might be a great potential in constructing optoelectronic nanodevices.