Biaxial tensile strain effects on photoluminescence of different orientated Ge wafers

The enhanced photoluminescence of direct transition is observed on (100), (110), and (111) Ge under biaxial tensile strain. The enhancement is caused by the increase in electron population in the Gamma valley. The shrinkage of energy difference between the lowest L valleys and the Gamma valley is responsible to the population increase on (100) and (110) Ge. For (111) Ge, the energy difference increases under biaxial tensile strain but the strain decreases energy difference between the electron quasi-Fermi level and the Gamma valley due to the small density of state of the lowest L valleys, and thus enhances direct recombination. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562589]