Carrier dynamics in blue and green emitting InGaN MQWs

Abstract

Spectrally and spatially‐resolved nonlinear optical techniques were combined with the photoluminescence spectroscopy to study carrier dynamics and photoluminescence efficiency in highly excited blue‐ and green‐emitting InGaN/GaN quantum wells. The differential transmission and transient grating techniques provided carrier lifetimes and diffusivity in the extended states with energies above the photoluminescence emission band and revealed their dependences on excess carrier density. At high excitation conditions, an increase of diffusivity led to the increase of nonradiative recombination rate, being more pronounced in the green QW structures with respect to the blue ones. Enhancement of these processes in the extended states has a strong impact on diminishing the photoluminescence efficiency in the localized states.

Impact of Alloy-Disorder-Induced Localization on Hole Diffusion in Highly Excited c -Plane and m -Plane ( In , Aleksiejūnas1, Nomeika2, Kravcov3 et al. 2020Phys. Rev. Applied

“…While the dependence D a (N ) in the thin c-plane MQW sample resembles those observed in other polar (In,Ga)N QW structures [33,45], the kind of behavior seen in the m-plane and thick c-plane samples is untypical. To better understand the processes behind it, we separately analyze the "low-density" region, where D(N ) decreases with increasing density, and the "high-density region," where the D(N ) dependence is opposite and increases with the excitation.…”

“…c-plane QW structures [34,45]. These facts suggest that the high diffusivity must be related to the thick layers and compositional disorder.…”

Impact of carrier diffusion on the internal quantum efficiency of InGaN quantum well structures

“…We reported previously on the negative correlation between the carrier lifetime and diffusivity in bulk GaN 44 and InGaN QWs. 45,46 We argued that such a dependence can be explained by carrier transport towards the dislocations that are known to be efficient non-radiative centres. 47 Such an assumption is feasible for heteroepitaxially grown InGaN QW structures with a high density of threading dislocations.…”

Enhancement of quantum efficiency in InGaN quantum wells by using superlattice interlayers and pulsed growth

“…The impact of the internal electrical field, however, cannot fully account for differences in IQE, especially at high carrier densities. Also, large PL peak shift can be caused by saturation of localized states at a low energy side of the PL spectrum [19][20][21][22]. Time-resolved FCA, PL, and DT measurements were carried out for a direct observation of carrier dynamics and discrimination between the radiative and non-radiative recombination pathways.…”