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Optical Absorption of Cr 4+ in GaAs:Cr
Author(s) -
Ulrici W.,
Kleinert P.
Publication year - 1985
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/pssb.2221290134
Subject(s) - ground state , photoionization , absorption edge , atomic physics , absorption (acoustics) , valence (chemistry) , phonon , absorption spectroscopy , coupling (piping) , electron , materials science , analytical chemistry (journal) , band gap , chemistry , molecular physics , physics , condensed matter physics , optics , ion , ionization , organic chemistry , quantum mechanics , chromatography , metallurgy
Optical absorption experiments are reported on p‐type GaAs:Cr:Zn from which the spectral shape of the absorption due to stable Cr 4+ is derived in the energy region from the onset at about 0.4 eV up to the GaAs absorption edge. This absorption is interpreted as due to the photoionization transition Cr 4+ + hv → Cr 3+ + hole vb superimposed by the simultaneously occurring transition Cr 3+ + hv → Cr 2+ + hole vb . Its spectral shape at T = 78 K can well be fitted by a calculated one taking into account the uppermost three valence bands, the 4 T 1 (F) ground state of Cr 3+ and the 5 T 2 ground state of Cr 2+ located within the gap, and the electron‐phonon coupling of these localized states. The fit yields the optical threshold energy E 3 = 0.68 eV and the broadening parameter Γ 3 = 0.24 eV of the Cr 4+ → Cr 3+ transition indicating a strong coupling of the 4 T 1 (F) state of Cr 3+ with TA phonons.