Dynamics of polarized photoluminescence in m-plane InGaN/GaN quantum wells

Abstract

Spectrally-, polarization-, and time-resolved photoluminescence ͑PL͒ experiments have been performed on 2.5 nm thick m-plane single InGaN quantum wells. It has been found that PL decay is mainly determined by nonradiative recombination through several types of recombination centers, while PL rise is largely affected by exciton transfer into localization minima. Prolonged PL rise times and time-dependent spectral shift were used to study exciton transfer into the localization centers. Characteristic time of the exciton transfer is 80-100 ps at lower temperatures and about 50 ps at room temperature, which corresponds to the exciton diffusion length of 200-500 nm. Degree of PL linear polarization was found to decrease at a similar rate. Decreased PL polarization for the localized excitons suggests that the localization centers are related to areas with relaxed strain.

Highly polarized photoluminescence and its dynamics in semipolar (202¯1¯) InGaN/GaN quantum well

“…The degree of the optical polarization is primarily defined by properties of the band structure, 4 however, it can be significantly affected by carrier localization. 5,6 Thus, data on the polarization degree is also important for studies of basic properties and localization effects in ternary nitrides of nonpolar and semipolar orientations. As yet, theoretical models do not always reproduce the experimental data on interlevel energies and optical polarization features of InGaN QWs.…”

“…Its dynamics may provide information on the carrier transfer from extended to localized states, and on symmetry properties of the localized states. 6 Therefore, dynamics of the polarization degree was also investigated for the studied 20 2 1 ð Þ QW. The temporal dependence of the polarization degree was calculated from PL transients measured for E?c and E k c proj polarizations.…”

Lateral carrier confinement in InGaN quantum-well nanorods

“…Nonetheless, the effects of nanostructures on the recombination of localized states have not been fully understood. It is known that the carrier diffusion lengths in InGaN/GaN QWs have been characterized to be in the order of 10 2 nm [58,59], which is comparable or even larger than the diameters of the nanorods used in previous studies. In these nanostructures, the carrier diffusion may be strongly confined in the lateral direction which should significantly modify the emission properties, which, in return, can affect the efficiency of white-light conversion.…”

Effects of reduced exciton diffusion in InGaN/GaN multiple quantum well nanorods

“…11,24 This thermally-activated carrier transport drives the excitons filling the low energy levels prior to the interband transition. The diameters of nanorods are close or smaller than the carrier diffusion length, [21][22][23] so that the carrier transport will be partially eliminated in nanorods.…”

“…11,24 This temperature dependence indicates the carrier transport is activated thermally. The carrier transport process, in a time scale of sub-nanosecond, [21][22][23] enables that photon-excited electrons and holes to recombine from the strongly-localized states in MQWs. In nanorods, the size effect has profound impacts on carrier transport process and the temporal evolution behavior of the emission in nanorods diverges from that in MWQs.…”