Defect-related luminescence from nanostructured Si layers in the 1.5-1.6 μm wavelength region

摘要

Silicon with high concentrations of deep states is considered as a promising material for the fabrication of light emitters in the infrared region. We develop the method in which deep states appear in Si as a result of crystal defect formation during Si growth on the surfaces covered with dense arrays of Ge nanoscale islands. The concentration of dislocations in the grown Si layers reaches an order of 10~(11) cm~(-2) or higher. Such layers can be referred to as nanostructured Si (ns-Si). Light emitting diodes fabricated on the base of the ns-Si produce infrared emission in the wavelength region from about 1.4 to 1.7 μm at room temperature. To study the radiative and nonradiative recombination processes in the ns-Si, we measured the dependence of photoluminescence (PL) on the excitation power density at several temperatures. The model of the band structure and density of states is offered which involves only one type of radiative deep states that are responsible for the PL peak in the region from 1.5 to 1.6 μm. The observed dependences are explained as a result of competition between multiphonon and Auger recombinations of carriers along with their thermal generation.