Luminescence properties of GeSn laser materials: Influence of buffered substrates

Time-resolved photoluminescence spectroscopy is used to measure the luminescence lifetime of two direct bandgap GeSn samples. The GeSn samples are similar in respect to the material properties, except for one being grown on a thin Ge-post-deposition annealed buffered layer, while the other is grown on a thick Ge virtual substrate. The total photoluminescence intensity and the lifetime of the samples are compared as a function of temperature between 20 and 300 K and pump fluence between 2.5×10¹³ and 1 × 10¹³ cm‾², showing little difference between the two samples. The luminescence lifetime varies only little with temperature, and calculations of the total photoluminescence intensity based on k·p theory are compared to experimentally attained values, yielding a good functional agreement vs temperature. The results point to the L-valley as one of the primary inhibiting factors of the photoluminescence intensity at non-cryogenic temperatures.