Indium distribution in InGaAs quantum wires observed with the scanning tunneling microscope

Abstract

The incorporation of In in the growth of crescent-shaped In0.12Ga0.88As quantum wires embedded in (AlAs)4(GaAs)8 superlattice barriers is studied in atomic detail using cross-sectional scanning tunneling microscopy. It is found that the In distribution in both the surface and the first subsurface layer can be atomically resolved in the empty- and filled-state images, respectively. Strong In segregation is seen at the InGaAs/GaAs interfaces, but neither an expected enhancement of the In concentration at the center of the quantum wire compared to the planar quantum well nor In clustering beyond the statistical expectation is observed.

Scanning tunneling microscopy contrast of isovalent impurities on the GaAs (110) surface explained with a geometrical model

“…For indium, typically, a bright contrast is observed in empty-state imaging conditions [20,[26][27][28], and for filled-state imaging at low indium concentrations there appears to be no indium contribution to the image [20]. This agrees with our simulations, which also show a bright contrast in the emptystate imaging and no indium contrast in the filled-state images.…”

“…This agrees with our simulations, which also show a bright contrast in the emptystate imaging and no indium contrast in the filled-state images. Some experimental results for indium in GaAs disagree with this and show bright spots in the filled-state imaging [28,29]; however, these results typically contain samples with very high concentrations of indium or are for systems with very high lattice strain such as quantum dots or rings.…”

Determination of the shape and indium distribution of low-growth-rate InAs quantum dots by cross-sectional scanning tunneling microscopy

“…The indium gradient is possible through growth processes such as segregation and strain related indium incorporation. 9,16 Both these mechanisms might be expected to lead to an indium gradient, resulting in a higher indium concentration in the top of the dot.…”

Annealing of InGaAlAs digital alloy studied with scanning-tunneling microscopy and filled-states topography

“…The indium-rich areas appear bright because the In atoms in the first subsurface layer cause the surface As atoms to protrude out of the surface plane. 10 the model described in Ref. 11, we find that a deviation of Ϫ7.5% and ϩ7.5% from the nominal indium concentration in the indium-poor and -rich areas, respectively, accounts for the observed corrugation modulation.…”