Modeling photoreflectance of quantum well heterostructures: A comprehensive approach

Abstract

Articles you may be interested inPhotoreflectance investigation of InAs quantum dashes embedded in In 0.53 Ga 0.47 As ∕ In 0.53 Ga 0.23 Al 0.24 As quantum well grown on InP substrate Interfaces in Ga x In 1 − x As y Sb 1 − y ∕ Al x Ga 1 − x As y Sb 1 − y multi-quantum-well heterostructures probed by transmittance anisotropy spectroscopy J. Appl. Phys. 98, 066107 (2005); 10.1063/1.2058214 Photoluminescence and photoreflectance study of InGaAs/AlAsSb quantum wells grown by molecular-beam epitaxy J. Appl. Phys. 95, 1050 (2004); 10.1063/1.1637936 Photoreflectance and photoluminescence spectroscopy of the lattice-matched InGaAs/InAlAs single quantum well J. Appl. Phys. 92, 920 (2002);We present a comprehensive approach to modeling the photoreflectance ͑PR͒ spectra of semiconductor quantum wells embedded in layered heterostructures. Near-gap PR spectra are obtained directly from the calculated variation of surface reflectance spectra induced by modulation of an internal electric field. The field-dependent reflectance spectra are themselves obtained from a transfer matrix model of a quantum well heterostructure ͑QWH͒ in which the quantum well layer is treated in detail using electric-field-dependent optical absorption calculations and all surrounding higher-gap layers are treated as lossless dielectric slabs. The model is described in detail and is applied to unstrained GaAs/AlGaAs and compressively strained InGaAs/GaAs single-well QWHs for which both experimental data and other calculations are available for comparison. This model can serve as a tool for interpretation of experimental PR spectra, and should be particularly useful for analysis of dense spectra with overlapping features that would be difficult to analyze using empirical fitting schemes. The approach can be used to model electroreflectance without modification.

Origin of additional spectral features in modulated reflectance spectra of 2-dimensional semiconductor systems

“…Some previous studies have considered these two cases separately, using a few discrete transitions and approximating the bandto-band transition by a broadened step function. 5,16 For the present problem at hand, the appropriate approach would be to use a model that naturally takes into account the infinite set of discrete transitions as well as the Sommerfeld factor modified band-to-band transitions. Such a formulation considering homogeneous broadening with Lorentzian lineshapes exists.…”

“…4 A more recent attempt at theoretical modelling of PR lineshapes in QWs has however completely ignored the possibility of additional transitions close to ground state n ¼ 1 exciton transition. 5 Verifying the presence of such additional PR spectral features in 2D systems and understanding their exact origins have become important in the context of materials of current research interest such as group III Nitride QWs and monolayer MoS 2 . If the exciton binding energy E b is small ($few meV) then inhomogeneous broadening of the transitions, arising from defects and impurity related band tailing, makes it difficult to observe any fine structure in the spectrum.…”