“S-shaped” temperature-dependent emission shift and carrier dynamics in InGaN/GaN multiple quantum wells

Abstract

We report temperature-dependent time-integrated and time-resolved photoluminescence (PL) studies of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition. We observed anomalous emission behavior, specifically an S-shaped (decrease–increase–decrease) temperature dependence of the peak energy (Ep) for InGaN-related PL with increasing temperature: Ep redshifts in the temperature range of 10–70 K, blueshifts for 70–150 K, and redshifts again for 150–300 K with increasing temperature. In addition, when Ep redshifts, the spectral width is observed to narrow, while when Ep blueshifts, it broadens. From a study of the integrated PL intensity as a function of temperature, it is found that thermionic emission of photocarriers out of local potential minima into higher energy states within the wells is the dominant mechanism leading to the thermal quenching of the InGaN-related PL. We demonstrate that the temperature-induced S-shaped PL shift is caused by a change in the carrier dynamics with increasing temperature due to inhomogeneity and carrier localization in the InGaN/GaN MQWs.

Small band gap bowing in In1−xGaxN alloys

“…shaped dependence is observed for In 0.89 Ga 0.11 N. This inverted S-shaped phenomenon has been observed previously in alloys such as GaInP [22], AlInAs [23], and Ga-rich InGaN [24], and in InGaN/GaN quantum wells [25], and is attributed to carrier localization. The FWHM of the PL of In 0.89 Ga 0.11 N shows a rapid increase below the temperature (~75K)…”

Exciton localization on basal stacking faults in a-plane epitaxial lateral overgrown GaN grown by hydride vapor phase epitaxy

“…This explanation is also consistent with the 3-4 meV blueshift and the vanishing of the low-energy tail of the BSF-related emission observed by Paskov et al 22 when increasing the excitation density. The blueshift part of the S-shaped temperature dependence is commonly observed in epitaxial type-I and type-II quantum wells 23,24 due to fluctuations of the well width by one or two monolayers. However, it is unlikely that quantum wells formed by stacking faults present such fluctuations because the distance between two changes in the stacking sequence is precisely determined by the type of the BSF: for instance, the width of I 1 stacking faults is exactly equal to 1.5c 0 , where c 0 is the unstrained lattice parameter of wurtzite GaN along the ͑0001͒ direction.…”

Double-scaled potential profile in a group-III nitride alloy revealed by Monte Carlo simulation of exciton hopping

“…4 Indium is demonstrated to smooth the chaotic band-tail potential induced by partial disorder in the nitride alloys due to composition fluctuations 5 and, thus, facilitates hopping of localized excitons at low temperatures. 6 An ''anomalous'' S-shaped temperature dependence of the photoluminescence ͑PL͒ band peak observed in InGaN, 7,8 AlGaN, 9 and AlInGaN [10][11][12] as well as W-shaped dependence of the full width at half maximum ͑FWHM͒ 10,13 are usually considered as a signature of exciton hopping. 14 -16 The following qualitative explanation of the anomalous temperature behavior of the emission band in semiconductors was proposed to interpret the observation of this phenomenon in InGaAs/InP single quantum wells.…”