Quantum-confinement-induced {Gamma}{r_arrow}{ital X} transition in GaAs/AlGaAs quantum films, wires, and dots

Journal Article · Wed Nov 15 04:00:00 EST 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.52.14664· OSTI ID:165821

Franceschetti, A; Zunger, A ^[1]

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1. National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

Large GaAs domains embedded in an Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As matrix act as potential wells for both electrons and holes, resulting in a direct band-gap system. When the GaAs domains become small, however, quantum-confinement effects may push the {Gamma}-like conduction-band state localized on GaAs above the {ital X}-like conduction-band state of the Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As alloy, leading to an indirect band-gap system. Using a pseudopotential band-structure method, as well as the conventional one-band effective-mass approximation, we investigate the nature of the direct{r_arrow}indirect ({Gamma}{r_arrow}{ital X}) transition in GaAs/Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As quantum films, wires, and dots. In the case of an {ital isolated} GaAs quantum structure embedded in AlAs, we find that the critical size for the onset of the {Gamma}{r_arrow}{ital X} transition increases from {similar_to}31 A in a two-dimensional film through {similar_to}56 A in a one-dimensional cylindrical wire to {similar_to}80 A in a zero-dimensional spherical dot. The interaction between GaAs quantum structures tends to {ital reduce} the critical size for the {Gamma}{r_arrow}{ital X} transition. We further study the effect of the alloy composition on the {Gamma}{r_arrow}{ital X} transition, finding that the critical size {ital decreases} when the Ga concentration of the alloy {ital increases}. In the case of spherical GaAs quantum dots embedded in an Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As alloy, we show that, as a function of the dot radius and the alloy composition, different alignments of the band-edge states lead to different regimes of the lowest-energy optical transition.

• OSTI ID: 165821
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 20 Vol. 52; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ARSENIDES
EFFECTIVE MASS
ELECTRONIC STRUCTURE
ENERGY-LEVEL TRANSITIONS
GALLIUM ARSENIDES
OPTICAL PROPERTIES
THIN FILMS