On optical polarization and charge carrier statistics of nonpolar InGaN quantum wells

Abstract

Abstractauthoren Optical polarization is a fundamental property of light emission from m‐plane InGaN quantum wells. It is a result of band structure, anisotropic strain, the degree of polarization depending on thermal occupation, and band‐filling of valence subbands. We analyze the optical‐polarized light of nonpolar samples at low and at room temperature over a wide range of excitation density. We observe that the measured energy separation and linewidth of the orthogonally polarized emission depend on carrier density, too. A consistent explanation of these effects is possible in the context of Fermi–Dirac statistics for a degenerate carrier density n>1017thinmathspacecm−3 and inhomogeneously broadened density of states. In addition, pulsed electroluminescence experiments were performed to validate our conclusions for optoelectronic devices based on nonpolar InGaN quantum wells.

Carrier-density-dependent recombination dynamics of excitons and electron-hole plasma in m -plane InGaN/GaN quantum wells

“…Note that we only consider the transition between the conduction band and the first valence band. It is a valid approximation because the energy splitting between the first and second valence bands in m-plane InGaN/GaN QWs (35 meV in the present sample as deduced from k·p simulations) [26] is larger than the thermal activation energy at 300 K. In addition, is the reduced Planck constant, and m 0 is the electron rest mass. Figure 2(a) evidences the influence of the n-type background doping on the radiative lifetime of the e-h plasma at 300 K. We see that τ r,e−h can be significantly reduced when increasing n 0 at low injection.…”

“…m e = 0.2 m 0 is the effective electron mass and m h = √ m m ⊥ is the geometric mean value of the in-plane effective hole mass in the first valence band. By using k·p simulations [26], we estimate the effective mass along the c axis to be m = 1.83 m 0 and the one in the perpendicular direction to be m ⊥ = 0.185 m 0 . Note that we only consider the transition between the conduction band and the first valence band.…”

The optical and structure properties of high-quality InGaN/GaN epilayers grown on miscut sapphire substrate

“…Therefore, such energy shifts of the different polarized light cannot be due to strain anisotropy and the VB separation. Thus, the blue-shift of the peak wavelength can be due to the band-tail filling effect by carriers 27 that is observed on the m-plane. Such band filling effects can be due to fluctuations of the band gap of inhomogeneous in distribution across the sample that creates localized states.…”

Temperature‐Dependent Polarized Photoluminescence from c‐plane InGaN/GaN Multiple Quantum Wells Grown on Stripe‐Shaped Cavity‐Engineered Sapphire Substrate

“…Although similar temperature dependence of peak positions of the two perpendicular components has been observed from m‐plane InGaN/GaN MQWs, the origin was not deeply discussed in the literature . Schade et al observed decreasing polarization ratios and increasing emission peak shifts from m‐plane InGaN/GaN MQWs with increasing carrier density at 10 K . Although the origin was explained in terms of carrier statistics in the valence band structures, these phenomena and explanation for them have not been reported for the conventional c‐plane InGaN/GaN MQWs due to intrinsic small splitting of top‐most subbands.…”