Photoluminescence due to inelastic scattering processes of excitons in a GaN thin film grown by metalorganic vapor phase epitaxy

Abstract

We have investigated photoluminescence (PL) properties of a high quality GaN thin film grown by metalorganic vapor phase epitaxy under intense excitation conditions in a wide temperature range from 10 to 300 K. It is found that there are two types of PL band peculiar to intense excitation conditions. In a low temperature region below 80 K, the exciton-exciton scattering dominates the PL, the so-called P emission.On the other hand, in a high temperature region above ~120 K, a PL band, which is different from the P emission, appears. The energy spacing between the new PL band and the fundamental A exciton linearly increases with an increase in temperature. In addition, the energy spacing is estimated to be zero at absolute zero temperature by extrapolation of the temperature dependence. These PL profiles indicate that the PL band observed in the high temperature regime originates from the exciton-electron scattering. . The well-known emission process is exciton-exciton scattering, the so-called P emission, in which one of two n = 1 excitons is scattered into a high-energy state with n ≥ 2, while the other is scattered into a photon-like state; the energy of which is lower than that of the n = 1 exciton state by the energy difference between the n = 1 and n ≥ 2 states. The P emission has been intensively studied in various wide-gap semiconductors: e.g., ), lightly-alloyed InGaN (Ref.[5]), CdS (Ref.[6]), ZnO (Ref. [7]), and CuI (Ref. [8]). On the other hand, there have been limited reports on the investigation of exciton-carrier scattering. In II-VI semiconductors [7,9,10] and cuprous halides [11], the characteristics of PL due to exciton-electron scattering were studied in a high temperature regime, which is called H emission. The exciton-electron scattering process is explained as follows. One electron around the bottom of the conduction band is scattered into a larger wavevector state, i.e., a hot electron, while one exciton in the first quantum (n = 1) state is scattered into a photon-like state; the energy of which is lower than that of the n = 1 exciton state by the energy difference between the initial and hot electron states. There are two specific features of the PL due to exciton-electron scattering. One is a low energy shift of the PL energy with an increase in excitation power because of an increase of effective temperature, which is similar to the P emission. The other is a linear temperature dependence of the en-

Large-kexciton dynamics in GaN epilayers: Nonthermal and thermal regimes

“…In fact the role of the inelastic exciton-exciton collision in the population redistribution in GaN has been reported by several autors. 24,25 An evaluation of the exciton-exciton scattering rate can be obtained by the dephasing time. 26) this contribution to the linewidth depends on the exciton density N X as Γ XX = β XX a 3 B E B N X , where a B is the exciton Bohr radius, E B the exciton binding energy and β XX a dimensionless efficiency factor which for GaN is between 5 and 7.…”

Evidence for Spatial Propagation of Photon-like Polaritons Generated by Exciton–Exciton Scattering in a GaAs/AlAs Multiple-Quantum-Well Structure

“…Thus, the photon-like LP is generated as the final state for the P emission. The P emission has been mainly observed in wide-gap semiconductors with large exciton binding energies such as ZnO, [2][3][4][5] CdS, 6) lightly-alloyed Zn x Mg 1-x O, 7) GaN, [8][9][10][11] lightly-alloyed In x Ga 1-x N, 12) and CuI. [13][14][15] The exciton-exciton scattering in quantum-well (QW) systems was reported in Zn x Cd 1-x Se/ZnSe, 16,17) ZnO/Zn x Mg 1-x O, 18) and GaAs/AlAs [19][20][21] multiple-QW (MQW) structures.…”

Spatially-Resolved Photoluminescence Study of Temperature Dependence of Exciton Inelastic Scattering Processes in a ZnO Thin Film

“…Subsequently, the photon-like LP is converted to the so-called P emission. 3) The P emission has been mainly observed in the following wide band-gap semiconductors in a low temperature region: ZnO, 3,4) CdS, 5,6) GaN, [7][8][9] In x Ga 1-x N, 10) and CuI. 11,12) In the exciton-electron scattering process under energy and momentum conservation, an electron around a conduction-band bottom is scattered to a hot electron.…”

“…On the other hand, an exciton with n=1 is scattered onto the photon-like LP leading to photon conversion, 3) the so-called H emission. 13) The electron contributing to exciton-electron scattering in undoped semiconductors is provided by thermal dissociation of excitons; therefore, the H emission is usually observed in a relatively high temperature region in wide band-gap semiconductors such as ZnO, 4) CdS, 5) GaN, 9,14) and cuprous halides (CuCl, CuBr, and CuI). 13) The excitonic system in ZnO is highly stable because of E b =60 meV.…”

“…In a relatively high temperature region, it is expected that the H emission due to exciton-electron scattering occurs. 4,9,13,14) The PL-peak energy of the H emission, E H , is given…”