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Optical properties of ion-implanted GaAs: The observation of finite-size effects in GaAs microcrystals

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dc.contributorVirginia Techen
dc.contributor.authorFeng, G. F.en
dc.contributor.authorZallen, Richard H.en
dc.contributor.departmentPhysicsen
dc.date.accessed2014-04-23en
dc.date.accessioned2014-05-07T15:37:03Zen
dc.date.available2014-05-07T15:37:03Zen
dc.date.issued1989-07en
dc.description.abstractWe have carried out reflectivity measurements, for photon energies from 2.0 to 5.6 eV in the electronic interband regime, for a series of unannealed ion-implanted GaAs samples which had been exposed to 45-keV Be+ ions at various fluences up to 5×1014 ions/cm2. The microstructure of the near-surface implantation-induced damage layer in these samples is known (from previous Raman work) to consist of a fine-grain mixture of amorphous GaAs and GaAs microcrystals, with the characteristic microcrystal size L of the microcrystalline component decreasing with increasing fluence (L=55 Å at 5×1014 cm-2). The optical dielectric function of each sample’s damage layer has been derived from the observed reflectivity spectrum by Lorentz-oscillator analysis. Then, by inverting the effective-medium approximation, we have extracted the dielectric function of the microcrystalline component (μ-GaAs) within the damage layer. The optical properties of μ-GaAs differ appreciably from those of the bulk crystal, the difference increasing with decreasing L. We find that the microcrystallinity-induced spectral changes are concentrated in the linewidths of the prominent interband features E1, E1+Δ1, and E2. These linewidths increase linearly and rapidly with inverse microcrystal size: Γμ=Γ0+AL-1, where Γ0 is the linewidth in the bulk crystal, Γμ is the linewidth in μ-GaAs, and A is a constant. For the E1 and E2 peaks, the experimentally determined value of A is such that the finite-size broadening (AL-1) is about 0.2 eV when L=100 Å. We propose a simple theory of the finite-size effects which, when combined with band-structure information for GaAs, semiquantitatively accounts for our observations. Small microcrystal size implies a short time for an excited carrier to reach, and be scattered by, the microcrystal boundary, thus limiting the excited-state lifetime and broadening the excited-state energy. An alternative uncertainty-principle argument is also given in terms of the confinement-induced k-space broadening of electron states.en
dc.description.sponsorshipTexas Instrumentsen
dc.description.sponsorshipVirginia Center for Innovative Technologyen
dc.identifier.citationFeng, G. F.; Zallen, R., "Optical properties of ion-implanted GaAs: The observation of finite-size effects in GaAs microcrystals," Phys. Rev. B 40, 1064 DOI: http://dx.doi.org/10.1103/PhysRevB.40.1064en
dc.identifier.doihttps://doi.org/10.1103/PhysRevB.40.1064en
dc.identifier.issn0163-1829en
dc.identifier.urihttp://hdl.handle.net/10919/47871en
dc.identifier.urlhttp://journals.aps.org/prb/abstract/10.1103/PhysRevB.40.1064en
dc.language.isoen_USen
dc.publisherAmerican Physical Societyen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectphysics, condensed matteren
dc.titleOptical properties of ion-implanted GaAs: The observation of finite-size effects in GaAs microcrystalsen
dc.title.serialPhysical Review Ben
dc.typeArticle - Refereeden

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