Impact of Diffusivity to Carrier Recombination Rate in Nitride Semiconductors: From Bulk GaN to (In,Ga)N Quantum Wells

We combined light induced transient grating and free carrier absorption techniques to investigate temporal and spatial carrier dynamics in nitrides. Inverse correlation of diffusivity and nonradiative recombination rate in GaN epilayers was ascribed to carrier diffusive flow to the internal boundaries of hexagonal grains and recombination on dislocations there, while the similar dependence in InGaN quantum wells (QWs) was a consequence of carrier delocalization caused either by carrier injection or thermal escape. Numerical modeling of recombination rates in light emitting diode structures with In content up to 13% revealed increasing with excitation nonradiative recombination rate which is a consequence of higher overall carrier mobility at higher densities. We propose the injection-enhanced in-plane diffusivity as the most probable mechanism explaining the increase of non-radiative losses in high power light emitting diodes (LEDs). (C) 2013 The Japan Society of Applied Physics