Long coherent dynamics of localized excitons in (In,Ga)N/GaN quantum wells

Abstract

We study the coherent dynamics of localized excitons in 100-periods of 2.5 nm thick (In,Ga)N/GaN quantum wells with 7.5% indium concentration, measured with spectroscopic resolution through two-pulse and three-pulse photon echoes at the temperature of 1.5 K. A long-lived coherent exciton dynamics is observed in the (In,Ga)N quantum wells: When the laser photon energy is tuned across the 43 meV-wide inhomogeneously broadened resonance line, the coherence time T2 varies between 45 and 255 ps, increasing with stronger exciton localization. The corresponding narrow homogeneous linewidths ranging from 5.2 to 29 µeV as well as the relatively weak exciton-phonon interaction (0.8 µeV/K) confirm a strong, quantum dot-like exciton localization in a static disordered potential inside the (In,Ga)N quantum well layers.

Robust Free Excitons in CH3NH3PbI3 Halide Perovskite Revealed by Four‐Wave Mixing

“…FWM is widely studied in covalent semiconductors and nanostructures based on them, such as GaAs, [6][7][8][9] CdTe, [10][11][12] ZnO, [13] GaN, [14] and in transition metal dichalcogenide monolayers. [15][16][17] To observe exciton resonances in these systems, it is necessary to use the highest quality crystals, since excitonic resonances in these materials are extremely sensitive to the presence of defects and impurities.…”

Superfluorescence of Sub-Band States in C-Plane In0.1Ga0.9N/GaN Multiple-QWs

“…C-plane InGaN/GaN quantum wells (QWs) as the prevailing active layer have been studied extensively due to their promising applications in group-III nitride semiconductor optoelectronic devices [ 1 , 2 , 3 , 4 ]. Commonly accepted explanations for emission features are the spatial localization of carriers due to random alloy fluctuations, indium compositional fluctuations and well width fluctuations [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], the quantum-confined Stark effect (QCSE) because it spatially separates electron and hole wave functions and reduces the wave function overlap in the QWs [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ] and the screening of the QCSE under a high excitation that affects the excitation density-dependent emission energy of InGaN/GaN MQWs, for example, a very strong emission from quantum-dot-like states [ 26 ], high energy emission band [ 27 , 28 , 29 ] and stimulated emission on the high-energy side in thick QWs [ 30 , 31 , 32 ].…”

Long-Lived Exciton Coherence in Mixed-Halide Perovskite Crystals

“…A powerful approach to reveal the effect of compositional substitution on the energy structure of semiconductors in the vicinity of the band gap is based on the analysis of the homogeneous line width of excitons at cryogenic temperatures. , The homogeneous exciton line width Γ 2 is influenced by various factors, including exciton–phonon interaction and the degree of exciton localization. In particular, for bulk semiconductors with a continuous energy spectrum, the exciton coherence time T 2 ∝ Γ 2 –1 is inherently short .…”