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Determination of critical thickness for defect formation of CdSe/ZnSe heterostructures by transmission electron microscopy and photoluminescence spectroscopy
Author(s) -
Litvinov D.,
Schowalter M.,
Rosenauer A.,
Daniel B.,
Fallert J.,
Löffler W.,
Kalt H.,
Hetterich M.
Publication year - 2008
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200824151
Subject(s) - photoluminescence , transmission electron microscopy , heterojunction , materials science , molecular beam epitaxy , analytical chemistry (journal) , spectroscopy , high resolution transmission electron microscopy , monolayer , substrate (aquarium) , epitaxy , layer (electronics) , optoelectronics , chemistry , nanotechnology , physics , chromatography , quantum mechanics , oceanography , geology
We report on the investigation of CdSe/ZnSe heterostructures by transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). CdSe layers with nominal thicknesses t CdSe between 0.5 and 8 monolayers (ML) were embedded in a ZnSe matrix and grown on a GaAs(001) substrate by molecular‐beam epitaxy at 280 °C. The Cd‐distribution was obtained from high‐resolution TEM lattice fringe images using composition evaluation by lattice fringe analysis technique. The measured minimum, average and maximum Cd‐concentrations and the overall CdSe contents in the layers increase with the nominal CdSe layer thickness and reach a constant value at t CdSe = 4 ML. The measured CdSe content in the regions with the maximal Cd‐concentration continues to increase for t CdSe ≥ 5 ML. The increasing of measured Cd‐concentrations/CdSe contents is correlated with a red shift of PL spectra. In the CdSe layers with t CdSe ≥ 5 ML, formation of defects is observed. The increasing density of defects and decreasing intensity of PL spectra with t CdSe suggest that the critical thickness for defect formation during CdSe growth on the ZnSe(001) is between 4 ML and 5 ML. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)