Carrier diffusion and recombination in highly excited InGaN/GaN heterostructures

Time‐resolved four‐wave mixing and photoluminescence techniques have been combined for studies of MOCVD‐grown InxGa1–xN/GaN/sapphire heterostructures with different indium content (0.08 < x < 0.15). In‐plane diffusion and recombination of spatially‐modulated carriers, confined in the front layer of 50‐nm‐thick InGaN, were monitored by a probe beam diffraction and provided an average value of a bipolar diffusion coefficient D ≈ 1–1.5 cm2/s and its dependence on the In content. A complete saturation of four‐wave mixing (FWM) efficiency vs excitation energy was found prominent in a layer with 10% of In. The latter effect of saturation correlated well with the dependence of quantum efficiency of stimulated emission on In content in heterostructures. Short decay times of stimulated emission (∼10 ps) measured by time‐resolved PL in highly excited structure allowed us to attribute the FWM saturation effect to the threshold of stimulated recombination. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)