Polarization anisotropy of the photoluminescence of M-plane (In,Ga)N/GaN multiple quantum wells

Abstract

We investigate the polarization anisotropy of the photoluminescence of an M-plane (11̄00) In0.1Ga0.9N/GaN multiple quantum well grown on γ-LiAlO2 (100) by molecular-beam epitaxy. In contrast to C-plane (0001) structures, a strong in-plane optical anisotropy with an energy-dependent polarization degree of up to 96% is observed for this M-plane sample. An apparent spectral shift of the emission with polarization angle is attributed to the impact of exciton localization on the polarization degree. The presence of localized states manifests itself further in the anomalous temperature dependence of the photoluminescence linewidth.

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

“…4 together with the (unpolarized) PL spectrum. We find a very high DOLP (>90%), which is in good agreement with other experimental data on mplane (In,Ga)N/GaN QWs [19,22,51]. Theoretically, based on continuum-like descriptions, at the VBE one would expect a very high DOLP for several reasons.…”

“…Theoretically, based on continuum-like descriptions, at the VBE one would expect a very high DOLP for several reasons. First, assuming growth along the y direction, the QW confinement lifts the degeneracy of the |X -and |Y -like valence band states due to their different effective masses along the growth direction [14,19,22]. Second, |X -and |Z -like states are energetically separated by the crystal field splitting energy in (In,Ga)N alloys [43].…”

“…Experimental studies on c-plane (In,Ga)N/GaN QW systems reveal that random alloy fluctuations lead to carrier localization effects, which can dominate the electronic and optical properties of these structures [23,24]. Clear experimental indications of the importance of alloy fluctuations on the properties of nonpolar (In,Ga)N QWs have also been presented [16,21,22]. To fully understand the structural, electronic, and optical properties of nonpolar (In,Ga)N QWs requires the use of a range of advanced experimental and theoretical techniques.…”

“…The spectral dependence of the DOLP of the emission was determined by measuring the PL spectra polarized in the plane parallel (I ) and perpendicular (I ⊥ ) to the c axis of the sample. Once the spectra are obtained, the DOLP is calculated from [22] …”

“…Additionally, (In,Ga)N QWs grown on nonpolar planes offer the possibility of acting as highly efficient sources of linearly polarized light [11,12,19], which may be of practical use in, e.g., back-lit liquid crystal displays [12]. The potentially high degree of optical linear polarization (DOLP) in a nonpolar QW originates mainly from differences in the effective hole masses along the growth direction, which leads to a lifting of the degeneracy of the highest lying p-like valence bands [19,22].…”