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Sub‐Bandgap Optical Electro‐Absorption in the Field of a P–N Junction
Author(s) -
Foygel M.,
Brenden E.,
Seguin J. H.,
Osipov V. V.
Publication year - 1997
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(199709)203:1<255::aid-pssb255>3.0.co;2-r
Subject(s) - attenuation coefficient , band gap , electric field , semiconductor , absorption (acoustics) , homogeneous , wavelength , doping , materials science , optics , field (mathematics) , condensed matter physics , molecular physics , optoelectronics , physics , quantum mechanics , mathematics , pure mathematics , thermodynamics
A sub‐bandgap light absorption coefficient α has been calculated as a function of light frequency ω for a semiconductor with a built‐in non‐homogeneous electric field of arbitrary shape. The electro‐absorption spectrum α(ω) is shown to possess the following features: a) as the energy of absorbed quanta ħω approaches a bandgap E g , the absorption coefficient α(ω) is close to that described by the Franz‐Keldysh law for the homogeneous effective field equal to the maximum field within the p–n junction; b) for smaller ω, the coefficient α drops more abruptly than in the case of a homogeneous field because it is determined by the lateral sides of the junctions where the local fields are weaker; and c) it is terminated at the point ω t = ( E g — Δ)/ħ, where Δ is the total potential barrier across the p–n junction. Possible applications for delta‐doped semiconductor superstructures are discussed. In particular, for materials with asymmetrical effective masses of the carriers ( m c — m lh ), the long‐wavelength tail of the absorption spectrum is more sensitive to the shape of the spatial distribution of donors than to that of acceptors.