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Point defects on the (110) surfaces of InP, InAs, and InSb: A comparison with bulk
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 7, 075332- p.Article in journal (Refereed) Published
Abstract [en]

The basic properties of point defects, such as local geometries, positions of charge-transfer levels, and formation energies, have been calculated using density-functional theory, both in the bulk and on the (110) surface of InP, InAs, and InSb. Based on these results we discuss the electronic properties of bulk and surface defects, defect segregation, and compensation. In comparing the relative stability of the surface and bulk defects, it is found that the native defects generally have higher formation energies in the bulk. From this it can be concluded that at equilibrium there is a considerably larger fraction of defects at the surface and under nonequilibrium conditions defects are expected to segregate to the surface, given sufficient time. In most cases the charge state of a defect changes upon segregation, altering the charge-carrier concentrations. The photothresholds are also calculated for the three semiconductors and are found to be in good agreement with experimental data.

Place, publisher, year, edition, pages
2006. Vol. 74, no 7, 075332- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95999DOI: 10.1103/PhysRevB.74.075332ISI: 000240238800083OAI: oai:DiVA.org:uu-95999DiVA: diva2:170402
Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2012-03-18Bibliographically approved
In thesis
1. Electronic Structure Calculations of Point Defects in Semiconductors
Open this publication in new window or tab >>Electronic Structure Calculations of Point Defects in Semiconductors
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Elektronstrukturberäkningar av punktdefekter i halvledare
Abstract [en]

In this thesis point defects in semiconductors are studied by electronic structure calculations. Results are presented for the stability and equilibrium concentrations of native defects in GaP, InP, InAs, and InSb, for the entire range of doping conditions and stoichiometry. The native defects are also studied on the (110) surfaces of InP, InAs, and InSb. Comparing the relative stability at the surface and in the bulk, it is concluded that the defects have a tendency to migrate to the surface.

It is found that the cation vacancy is not stable, but decomposes into an anion antisite-anion vacancy complex. The surface charge accumulation in InAs is explained by complementary intrinsic doping by native defects and extrinsic doping by residual hydrogen.

A technical investigation of the supercell treatment of defects is performed, testing existing correction schemes and suggesting a more reliable alternative. It is shown that the defect level of [2VCu-IIICu] in the solarcell-material CuIn1-xGaxSe2 leads to a smaller band gap of the ordered defect γ-phase, which possibly explains why the maximal efficiency for CuIn1-xGaxSe2 has been found for x=0.3 and not for x=0.6, as expected from the band gap of the α-phase.

It is found that Zn diffuses via the kick-out mechanism in InP and GaP with activation energies of 1.60 eV and 2.49 eV, respectively. Explanations are found for the tendency of Zn to accumulate at pn-junctions in InP and to why a relatively low fraction of Zn is found on substitutional sites in InP.

Finally, it is shown that the equilibrium solubility of dopants in semiconductors can be increased significantly by strategic alloying. This is shown to be due to the local stress in the material, and the solubility in an alloy can in fact be much higher than in either of the constituting elements. The equilibrium solubility of Zn in Ga0.9In0.1P is for example five orders of magnitude larger than in GaP or InP.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. viii, 92 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 316
Keyword
Physics, electronic structure calculations, point defects, semiconductor, formation energy, equilibrium solubility limit, thermodynamic equilibrium concentration, transfer levels, negative-U, (110) surface, diffusion, activation energy, solar cells, Fysik
Identifiers
urn:nbn:se:uu:diva-7926 (URN)978-91-554-6916-0 (ISBN)
Public defence
2007-06-08, Siegbahnsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2009-05-28Bibliographically approved

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Höglund, AndreasCastleton, ChristopherJohansson, BörjeMirbt, Susanne

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