Improvement in photoluminescence efficiency of Si1−xGex alloy nanocrystals embedded in SiO2 matrices by P doping

The effects of P doping on photoluminescence (PL) properties of Si1−xGex alloy nanocrystals (nc-Si1−xGex) embedded in SiO2 thin films were studied. P doping resulted in a drastic decrease in the electron spin resonance (ESR) signals, which are assigned to the Si and Ge dangling bonds at interfaces between nc-Si1−xGex and matrices (Si and Ge Pb centers). It was found that, with increasing P concentration, the signal from Ge Pb centers is first quenched, and then the quenching of the signal from Si Pb centers starts. The quenching of the ESR signals was accompanied by a drastic enhancement of PL intensity. By further increasing P concentration, PL intensity became weaker. In this P concentration range, optical absorption due to the intravalley transition of free electrons generated by P doping appears.