Substrate orientation effect on potential fluctuations in multiquantum wells of GaAs∕AlGaAs

Abstract

Suppression of nonradiative recombination process in directly Si-doped InAs/GaAs quantum dots J. Appl. Phys. 110, 103511 (2011) GaN directional couplers for integrated quantum photonics Appl. Phys. Lett. 99, 161119 (2011) Room temperature spin filtering effect in GaNAs: Role of hydrogen Appl. Phys. Lett. 99, 152109 (2011) Carrier localization and related photoluminescence in cubic AlGaN epilayers J. Appl. Phys. 110, 063517 (2011) Additional information on J. Appl. Phys. The photoluminescence ͑PL͒ technique as a function of temperature and excitation intensity was used to study the optical properties of multiquantum wells ͑MQWs͒ of GaAs/ Al x Ga 1−x As grown by molecular beam epitaxy on GaAs substrates oriented in the ͓100͔, ͓311͔A, and ͓311͔B directions. The asymmetry presented by the PL spectra of the MQWs with an apparent exponential tail in the lower-energy side and the unusual behavior of the PL peak energy versus temperature ͑blueshift͒ at low temperatures are explained by the exciton localization in the confinement potential fluctuations of the heterostructures. The PL peak energy dependence with temperature was fitted by the expression proposed by Pässler ͓Phys. Status Solidi B 200, 155 ͑1997͔͒ by subtracting the term E 2 / k B T, which considers the presence of potential fluctuations. It can be verified from the PL line shape, the full width at half maximum of PL spectra, the E values obtained from the adjustment of experimental points, and the blueshift maximum values that the samples grown in the ͓311͔A / B directions have higher potential fluctuation amplitude than the sample grown in the ͓100͔ direction. This indicates a higher degree of the superficial corrugations for the MQWs grown in the ͓311͔ direction.

Spin-dependent analysis of homogeneous and inhomogeneous exciton decoherence in magnetic fields

“…At low temperatures, excitons can be trapped into these fluctuations and, by increasing T L , they progressively diffuse and recombine radiatively from higher energy states [27]. By increasing the laser power density [26] the band-gap fluctuations are effectively screened reducing E p , as confirmed in Figs. 2(a), 2(b) and 2(c).…”

“…Here, p is a parameter related to the shape of the electron-phonon spectral function [24,26]. The deviation E p of the theoretical expectations and the experiment, is produced by local band-gap fluctuations provoked by interface roughness [26]. At low temperatures, excitons can be trapped into these fluctuations and, by increasing T L , they progressively diffuse and recombine radiatively from higher energy states [27].…”

“…where E g = 1.519 eV is the GaAs energy band gap at T L = 0 K, and E e 1 + E h 1 = 98 meV is the extra energy given by the QW confinement, α = 5.405 × 10 −4 eV/K, [25] ≡ hω LO /k B with hω LO = 36 meV for GaAs, while p = 2.5 for 60 W/cm 2 and p = 2.45 for 2 × 10 4 W/cm 2 . Here, p is a parameter related to the shape of the electron-phonon spectral function [24,26]. The deviation E p of the theoretical expectations and the experiment, is produced by local band-gap fluctuations provoked by interface roughness [26].…”

“…where σ is the standard deviation of the local band-gap fluctuations [26,29], and β = [1 + (λ μ /λ g ) 2 ] −1/2 ∈ (0, 1] depends on the ratio of the characteristic length of the carriers transport λ μ with respect to the correlation length scale of the fluctuations λ g , and ponders the trapping efficiency: 8) and Gaussian functions (dashed lines) according to Eq. ( 9).…”

Power- and temperature-dependent photoluminescence investigation of carrier localization at inverted interface transitions in InAlAs/InP structures

“…12) Carrier localization is a lovely phenomenon in quantum well (QW) structures, which can be formed by the impurities, lattice disorder, layer thickness or composition variation. [13][14][15] In our recent study, 12) we showed that the presence of localized carriers could be ascribed to the energy potential modulation associated with the indium cluster formation and PZ field.…”