Enhanced photoluminescence caused by localized excitons observed in MgZnO alloy

Abstract

Photoluminescence spectroscopy and positron annihilation spectroscopy probe of alloying and annealing effects in nonpolar m -plane ZnMgO thin films Appl. Phys. Lett. 96, 151904 (2010);Temperature-dependent photoluminescence of MgZnO alloy film has been studied, and it is found that the emission intensity increases significantly at a certain temperature range and then decreases when increasing temperature further. The anomalous increase is resulted from the localized excitons in MgZnO alloy, as revealed by the enhanced second-order longitudinal optical phonon in the Raman spectrum of the MgZnO film. A schematic model was suggested to depict the carrier transportation process in the MgZnO film considering the existence of localized exciton states. The results reported in this paper indicate that localized excitons in MgZnO alloy can result in greatly enhanced emission efficiency, which is eagerly wanted for the application of ZnO-based materials in high-efficiency light-emitting devices.

Investigation of localized and delocalized excitons in ZnO/ZnS core-shell heterostructured nanowires

“…The localized states can expand the electronic density of state (DOS) to form an exponential tail instead of the sharp conduction and valance band edges. Localized states can be found in the semiconductor quantum structures and has become one of the characteristics which have been demonstrated to be responsible for the high emission efficiency of a variety of semiconductor composites [2][3][4]. For example, in the case of dilute nitride semiconductors, the localized excitons always present a socalled "S-shape" peak position feature obtained from the temperature-dependent photoluminescence (TDPL) measurement and a "valley shape" of full width at half maximum (FWHM) [1,5].…”

“…In this paper, through the growth of ZnO/ ZnS core-shell heterostructured NWs, we have introduced localized states in the core-shell interface between the ZnO and ZnS. After subsequent thermal treatments, the optical properties of the localized excitons have been discussed based on laser spectroscopy [1][2][3][4][5][6][7][8]. The underlying physical mechanism of the change of localized excitons after thermal treatments has also been proposed and discussed in detail.…”

Effects of phosphorus doping by plasma immersion ion implantation on the structural and optical characteristics of Zn0.85Mg0.15O thin films

“…25 A peak at 3.452 eV was observed for the sample annealed at 900 C, which can be attributed to the delocalized exciton; this peak was also observed in as-annealed samples. 20,26,27 In the case of the implanted sample annealed at 1000 C, this peak was replaced by the localized exciton peak around 3.422 eV. 20,26,27 The difference between the localized and delocalized excitons can be described in terms of the wave function.…”

“…20,26,27 In the case of the implanted sample annealed at 1000 C, this peak was replaced by the localized exciton peak around 3.422 eV. 20,26,27 The difference between the localized and delocalized excitons can be described in terms of the wave function. The wave function of a delocalized exciton is always a propagating wave, while that of a localized exciton decays with distance.…”

Biexciton emission from sol-gel ZnMgO nanopowders

“…3,[6][7][8][9] There is also a large potential for the development of light-emitting devices operating in the UVto-deep-UV spectral range using Zn 1−x Mg x O ternary alloy semiconductors as an active layer in quantum-well structures. [10][11][12] In ZnO quantum-well, the binding energy of biexcitons enhance significantly. In particular, the biexciton binding energy in ZnO quantum-well can be comparable to thermal energy of room-temperature ͑RT͒, indicating the possibility of biexciton lasing even at RT.…”