Spatial evolution of inelastic scattering of high-density excitons in GaSe crystals

Ultrafast spectroscopy of stimulated emission in single ZnO tetrapod nanowires

“…Let us first consider the spectral shifts, the blue shift with increasing excitation intensity and the red shift with increasing time. The blue shift of the exciton resonance with increasing excitation intensity previously reported in ZnCdSe/ZnSSe quantum well structures was attributed to the exciton-exciton exchange effect [21], while the red shift of the free exciton band with increasing time in GaSe crystals was attributed to the phase space filling effect and the increase of the exciton self-energy due to exciton-exciton collisions [17].…”

“…However, due to the entirely different material properties of inorganic semiconductors and conjugated polymers, it is unlikely that the same explanations of the red shift and spectral narrowing would be valid in ZnO. While carrier dynamics was previously studied in various inorganic samples [17][18][19][20][21][22][23], none of the previously reported experimental results fully agree with the effects found in ZnO tetrapod nanowires.…”

“…Carrier dynamics upon ultrafast excitation were previously studied in different semiconductor crystals [17], epilayers [18], quantum wells [19][20][21], quantum wires [22], and nanocrystals [23,24]. Upon excitation with 120 ps pulses, emission spectra from free excitons in GaSe single crystals (at 2 K) exhibited a small red shift and spectral narrowing (on the hundreds of ps scale) which was attributed to the phase-space filling effect and an increase of the exciton self-energy [17]. A red shift of the spontaneous emission in ZnCdSe epilayers with increasing time was attributed to band-filling effects [18].…”

Pool–Frenkel thermoelectric modulation of exciton photoluminescence in GaSe crystals

“…1, which is typical for the PL spectra measured at different temperatures. As seen, the PL is determined by the resonant exciton emission in GaSe crystals [22][23][24][25][26]. The PL spectrum obtained at T¼50 K for an applied field of 1.6 Â 10 5 V/m is given in Fig.…”

“…It is seen from this spectrum that the PL consists of intrinsic and extrinsic regions. In the intrinsic region, there are four peaks attributed to direct free excitons (DFE, peak A), direct bound excitons (DBE, peak B), indirect free excitons (IFE, peak C) and indirect bound excitons (IBE, peak D), while the extrinsic region is composed of emission bands related to donor-acceptor, impurity level-valance band transitions [26][27][28]. PL spectra measured at different temperatures and applied fields were fit using Gaussians from which the energy positions and FWHM of different bands were determined.…”