Numerical simulation of the temperature dependence of photoluminescence in strained-Si_1−xGe_x/Si heterostructures

In previous work it has been shown that the decay in photoluminescence from Si/strained-Si_1−xGe_x/Si quantum wells at temperatures over 100 K is controlled by surface recombination and that the photoluminescence intensity can be increased by over an order of magnitude by surface passivation. These results had been explained only by a simple phenomenological model, which could not explain why at high pump power density the observed luminescence was constant from 77 to 250 K. This paper uses a two-carrier heterojunction device simulator to determine the carrier profiles during optical pumping. The profiles are used to understand quantitatively luminescence as a function of temperature and pump power density without making the over-simplifying assumptions required for analytical modeling. Surface recombination velocities over 10³ cm/s drastically affect the results, and Auger recombination plays an important role at high pump power density.