Photoluminescence from exciton-exciton scattering in a lightly alloyed InGaN thin film under intense excitation conditions

Abstract

We have investigated the photoluminescence properties of a lightly alloyed In0.02Ga0.98N thin film at 10 K under intense excitation conditions. A photoluminescence band (P band) peculiar to the intense excitation condition has been clearly observed. The excitation-power dependence of the P-band intensity exhibits an almost quadratic behavior, accompanied by a threshold-like appearance. The threshold-excitation power for the P band is very low: ∼3kW∕cm2. At the threshold excitation power, the energy of the P band is lower than the energy of the n=1 A free exciton by the energy difference between the n=1 and n=2 exciton states. The results described above indicate that the P band originates from exciton-exciton scattering. Furthermore, we have confirmed the existence of optical gain leading to stimulated emission in the energy region of the P band by using transmission-type pump-probe spectroscopy.

Photoluminescence dynamics of exciton-exciton scattering in a lightly alloyed InGaN thin film

“…The luminescence mechanism of InGaN has been discussed from an aspect of exciton localization due to spatial fluctuations of alloy potentials. 12,13 In our previous work, 11 we demonstrated that the exciton-exciton scattering process occurs in a lightly alloyed In 0.02 Ga 0.98 N thin film under a considerably low excitation power in comparison with the case of GaN. A possible explanation for this phenomenon is as follows.…”

“…The origin of the PL band that is observable at the excitation power of 0.05I 0 is weakly localized excitons due to random alloy potentials. 11 suddenly appears at the excitation power of 0.1I 0 ͑ϳ3 J / cm 2 ͒, where the vertical dashed line labeled E P2 indicates the peak energy ͑3.411 eV͒ of the P band. The energy spacing between the A-exciton energy ͑E A ͒ and E P2 is 20 meV.…”

“…This exciton-exciton scattering process causes the so-called P emission that has been mainly investigated in wide gap semiconductors: e.g., CdS, 2 ZnO, 3,4 CuI, [5][6][7] GaN, [8][9][10] and lightly alloyed InGaN. 11 Recently, InGaNbased optoelectronic devices have been significantly developed in the wavelength region from near ultraviolet to green light. The luminescence mechanism of InGaN has been discussed from an aspect of exciton localization due to spatial fluctuations of alloy potentials.…”

Photoluminescence from exciton‐electron inelastic scattering in a GaAs/AlAs multiple‐quantum‐well structure

“…Note that inelastic scattering of excitons produces an optical gain leading to stimulated emission, which is a merit in applications. The most typical process is exciton-exciton inelastic scattering that has been intensively studied in various wide gap semiconductors: e.g., GaN [2,3], lightly-alloyed InGaN [4], CdS [5], ZnO [6], and CuI [7]. In the inelastic scattering process of two n=1 excitons, where n denotes the quantum number of the hydrogenic exciton series, one is scattered into a higher-energy exciton 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.…”

Photoluminescence due to exciton–exciton scattering in a GaAs/AlAs multiple quantum well

“…In the scattering process of two n ¼ 1 excitons, one is scattered into a high-energy exciton state with nX2, while the other is scattered into a photon-like state under energy and momentum conservations. This scattering process causes the so-called P emission that has been mainly investigated in II-IV semiconductors with large exciton binding energies, such as ZnO [1] and ZnO/ZnMgO multiple quantum wells (MQWs) [2], and recently in III-V nitride semiconductors [3]. Although numerous studies of photoluminescence (PL) properties of GaAs/AlGaAs MQWs have been reported, there has been no clear evidence for the occurrence of the exciton-exciton scattering process until now.…”