Infrared photoluminescence from Si/Ge nanowire grown Si wafers

This paper investigates the enhancement of room temperature (RT) infrared (IR) photoluminescence (PL) from Si/Ge nanowire (NW) grown silicon (Si) wafers. The NW grown wafers were treated by an acid atmosphere consisting of vapor of hydrofluoric HF and HNO3 chemical mixture. The treatment modifies the surface particularly at defect sites such as pits, dislocations and stacking faults as well as NW surfaces by etching and forming oxides. This process can induce a passivated crystalline Si surface where band-to-band (BB) emission is the dominant property. Strong signals are observed at sub-band gap energies when the treatment results in disordered surface with oxygen related defects. IR PL is a competitive property between the Si BB transition and sub-gap emission which is mainly attributable to defects and partly to Ge dots. The enhancement in BB and deep-level PL was discussed in terms of strain, impurities, Ge dots and oxygen diffusion. The results demonstrate the effectiveness of the method in enhancing and tuning IR PL properties for possible applications.