The Role of Silicon Monohydride and Dihydride in the Photoluminescence of Porous Silicon and Photoluminescence of Porous Silicon Buried Underneath Epitaxial GaP

ABSTRACTThermal annealing studies of the photoluminescence (PL) intensity and Fourier-transform infrared (FTIR) spectroscopy have been performed concurrently on porous Si. A sharp reduction in the PL intensity is observed for annealing temperatures > 300 °C and this coincides with desorption of hydrogen from the SiH2 surface species. The role of silicon hydride species on the photoluminescence intensity has been studied. The surfaces of luminescent porous Si samples were converted to a predominate SiH termination using a remote H-plasma. The as-passivated samples were then immersed in various concentrations of hydrofluouric solutions to regulate the recovery of SiH2 termination on the surface. Photoluminescence measurements and transmission Fourier-transform infrared spectroscopy have shown that predominant silicon monohydride (SiH) termination results in weak photoluminescence. In contrast, it has been observed that the appearance of silicon dihydride (SiH2) coincides with an increase in the photoluminescence intensity. To achieve electroluminescence it will be beneficial to generate carriers with sufficient energy to populate the states of the quantum-confined Si structures. A viable method to accomplish this is to utilize a wide-bandgap heterojunction injector such as GaP. Toward that end we report the successful formation of porous Si buried underneath GaP islands and we demonstrate that the buried porous Si layer exhibits strong photoluminescence.