Longitudinal‐optical phonon broadening due to nitrogen atom incorporation in InGaAsN/GaAs quantum wells

Abstract

We present a study of the optical properties of double quantum wells of In 0.3 Ga 0.7 As 1-x N x /GaAs. The nitrogen composition, x, lies between 2 10 -3 and 9.5 10 -3 . Temperature dependence of time integrated photoluminescence (PL) and time-resolved PL have been investigated. The temperature dependences of the PL energy and the linewidth are correlated, and they show that the carriers are localised at low temperature. Consistently the energy dependence of decay time across the PL line is analysed in terms of mobility edge. The carrier localisation at low temperature is due to alloy disorder in the wells which induces potential fluctuations. The PL linewidth increases with temperature. This linewidth is also strongly increased by the increase of the N composition. We attribute this behaviour to an enhanced coupling of the carriers with LO phonons. We deduce from these results that N incorporation increases the polar character of the III-V compound. 1 Introduction The physics of III-(V,N) alloys is currently living a tremendous activity due to the dramatic red-shift that the band gap of these alloys experiences when the amount of nitrogen incorporated in the crystal increases. This paves the way to potential applications in the domain of longwavelength lasers [1] and high-performance solar cells [2]. The great interest of (Ga,In)(N,As) alloys is the possibility to realise quantum structures emitting light close to 1.55 µm, and, lattice matched on GaAs substrates. This lattice matched is crucial to reduce the density of non radiative defects, and to increase the quantum efficiency of these systems. Lasers operation at 1.55 µm has been obtained [3] using such quaternary alloys. However, the physical properties of these systems are still poorly known and a lot of points need to be clarified such as recombination dynamics, localisation effects and carrier coupling to longitudinal-optical (LO) phonons.In this work, we have investigated the temperature dependence of the optical properties of In 0.3 Ga 0.7 As 1-x N x /GaAs QWs. These experiments show that the low temperature radiative recombination is dominated by localised carriers. Above some critical temperature (varying from sample to sample) carriers are delocalised and we show that increasing the N composition strengthens the coupling between carriers and LO phonons.

Investigation of the localization effect in InGaNAs/GaAs SQWs using the LSE model

“…The broadening is combinations due to both inhomogeneous distribution of localized carriers by earlier parameters and impurity and phonon scattering (Eq. (8)) by the best‐chosen Γ 0 , η A , η LO , with LO phonon energy ħω LO = 35 meV 23. The value of η A is 1.2 × 10 −3 meV/K in all samples, which is small compare to the η LO in nitride semiconductors 9.…”

“…Therefore, the effective full width at half‐maximum (FWHM) energy of the luminescence peak is determined by calculating the convolution of the shape of the luminescence spectrum, $N{{\left( {E,T} \right)} \mathord{\left/ {\vphantom {{\left( {E,T} \right)} {\tau _{\rm r} }}} \right. \kern-\nulldelimiterspace} {\tau _{\rm r} }}$ , resulting from the inhomogeneous distribution of localized carriers and broadening duo to the impurity and phonon scattering 23: where Γ 0 is due to impurity/imperfection scattering and the second term due to phonon scattering, where η A and η LO are the acoustic‐phonon and longitudinal optical (LO)‐phonon scattering coefficients, respectively; ħω LO is the characteristic energy of the LO‐phonon.…”

Nitrogen induced localised-state ensemble effect on multi quantum well GaInNAs with low indium concentration

“…The luminescence linewidth due to the thermal redistribution of carriers can be applied within the LSE in equation (7), in which the convolution shape calculation of the luminescence spectrum depends on broadening due to the acoustic phonon scattering coefficient, σ A , longitudinal optical (LO)phonon scattering coefficient, γ LO , impurity/ imperfection scattering, Γ 0 , and from the inhomogeneous distribution of localised carriers, which can be determined by [43,44]:…”