Well-width-dependent carrier lifetime in AlGaN∕AlGaN quantum wells

Abstract

A set of Al0.35Ga0.65N∕Al0.49Ga0.51N multiple quantum wells (MQWs) with fixed barrier width and well widths varying from 1.65to5.0nm has been grown by metal-organic chemical vapor deposition. Carrier dynamics in the MQWs were studied using time-resolved photoluminescence (PL) spectroscopy and light-induced transient grating (four wave mixing) technique. The authors observed that the lifetime of nonequilibrium carriers (excitons) increases with decreasing well width and interpreted the effect by stronger localization preventing their migration to nonradiative recombination centers. Meanwhile the radiative decay time is also influenced by screening of the built-in electric field, which spatially separates the electrons and holes. It is shown that this effect affects the initial part of PL intensity decay after pulsed excitation. It becomes more pronounced with increase in the initial carrier density but saturates when the carrier density is high enough to completely screen the built-in electric field. The screening effect on PL decay is stronger in wider quantum wells.

Influence of Electric Field and Carrier Localization on Carrier Dynamics in AlGaN Quantum Wells

“…The model of strong localization is also consistent with the unusual carrier lifetime dependence on QW width measured in the same samples and reported in Ref. [5], where longer carrier lifetimes were observed in narrower QWs. Such behavior was attributed to stronger localization.…”

Direct study of nonlinear carrier recombination in InGaN quantum well structures

“…2) showed that carrier lifetime was the longest in the thinnest QWs (~2.7 ns at the lowest excitation) and the shortest in the thickest QW (~1.1 ns). These features we attribute to the effect of carrier localization due to well thickness fluctuations in the thin QWs (in our case, for d = 5.5 nm) (a similar effect was observed in AlGaN/AlGaN QWs [10]). Carrier localization prevents carrier migration to nonradiative recombination centers, therefore weaker localization in the thicker wells leads to shorter carriers lifetimes (we assume that the trap density is similar in three structures).…”

Efficiency droop in high‐Al‐content AlGaN/AlGaN quantum wells

“…As demonstrated for this set of samples in Ref. [14], the carrier lifetime at room temperature increases with decreasing the well width. This is an indication that the dominant origin of the localization is the well width fluctuations.…”