Influence of the quantum-well thickness on the radiative recombination of InGaN/GaN quantum well structures

Abstract

Temperature-dependent photoluminescence (PL) measurements are performed on In0.23Ga0.77N/GaN single-quantum-well structures with different well thickness. Based on a band-tail model, the exciton localization effect is studied. The exciton localization effect is enhanced by increasing quantum-well thickness up to 2.5 nm. If the quantum-well thickness is further increased to above 2.5 nm, the exciton localization effect becomes weak. Finally, when the quantum-well thickness is increased to 5 nm, the exciton localization effect cannot be observed. In addition, the PL intensity decreases monotonically with increasing the quantum-well thickness. In connection with an excitation-power dependent PL measurement, the result of the quantum-well thickness dependent PL intensity can be attributed to quantum confined Stark effect, which becomes particularly strong in the wide quantum-well structure. Based on our optical investigation, the presented article indicates that the emission mechanism is dominated by the exciton localization effect in the thin quantum-well structures, while the quantum confined Stark effect dominates the radiative recombination in the wide quantum-well structures. Since understanding the emission mechanism is very important for further improving the performance of an InGaN/GaN-based optical device, the presented results in this article should be highly emphasized.

Correlation between optical properties surface morphology of porous silicon electrodeposited by Fe 3+ ion

“…This S-shape behavior has already been observed by several authors [30][31][32][33] and has been attributed to localized exciton (LE) by potential fluctuations induced by random distribution of impurities, defects and alloy disorder in samples [34]. The S-shape disappears in the case of PSF22 sample where E PL (T) presents a temperature variation according to BoseEinstein model [35] (See Fig.…”

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

“…While all presented observations are valid for all of these samples, a particular set of samples was chosen exhibiting a weak QCSE-caused shift with excitation power density. 5,7,8 This choice eases an understanding of the reported phenomena, as none of the observations need to be uncoupled from additional dynamic processes imposed by the (de-)screening of the QCSE. In addition, a complete multi quantum well (MQW)-LED structure with n-and p-doped layers and commercial-grade QWs of similar thickness and composition was investigated.…”

“…First, the QW ground-state transition shifts by around 20 meV towards higher energies indicating a commonly reported weak QCSE. [4][5][6][7][8] At the same time, a significant broadening and an apparent asymmetry of the emission band are observed, which indicates band-filling. 20,21 Second, an additional, broad peak is observed at much higher energies, which we call the Confined Hole Continuum (CHC) luminescence.…”

“…[1][2][3] However, both device types suffer from a distinct efficiency reduction towards the green spectral range, despite the better confinement properties of energetically deeper QWs. Established reasons for this matter include a reduced electron-hole-overlap in the QWs due to the quantumconfined Stark effect (QCSE) [4][5][6][7][8] and general difficulties in growing homogeneous InGaN material. [9][10][11][12][13][14][15] Also high pumping conditions are known to cause a further reduction of the efficiency that is attributed to Auger recombination.…”

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

“…Nevertheless, at low temperatures, energy dependent radiative decay times for InGaN/GaN QWs are quoted [15][16][17][18] to be $10 s of nanoseconds compared with exciton decay times in GaAs/AlGaAs QWs $100 s of picoseconds. 19 It is widely accepted 18,[20][21][22][23][24] that the carrier localisation can, to a large extent, overcome non-radiative recombination associated with defects. However, the role of carrier localisation 25,26 in the process responsible for efficiency reduction at high carrier densities, the so-called efficiency droop, 27,28 is still the subject of extensive discussion.…”