Cross-sectional scanning tunneling microscopy of GaAsSb/GaAs quantum well structures

Abstract

We have used cross-sectional scanning tunneling microscopy ͑STM͒ to perform nanometer-scale characterization of compositional structure and interfacial properties within GaAs 1Ϫx Sb x /GaAs double-quantum well structures. An algorithm has been devised based on analysis of strain effects in STM data to obtain detailed, quantitative compositional profiles within alloy layers. Using this and other analysis techniques, we have assessed the influence of group V anion soaks at each heterojunction interface on interface roughness and abruptness. An As soak at the GaAs-on-GaAs 1Ϫx Sb x interfaces reduces interface roughness but leads to a slight loss of abruptness at the interface, while an AsϩSb soak at GaAs 1Ϫx Sb x-on-GaAs interfaces improves abruptness while leaving interface roughness largely unaffected. Significant compositional grading at the nanometer scale is observed within the GaAs 1Ϫx Sb x layers.

Effects of Gas switching sequences on GaAs/GaAs1−ySby superlattices

“…If the conditions in those studies for the pseudomorphic growth of GaAs 1Ày Sb y layers were extrapolated from thick layer growth studies, similar discrepancies in the alloy composition between the projected and realized alloy composition, observed in the present study, would exist. Higher Sb content layers were also grown within a SL structures by MBE, using elemental Sb [10].…”

“…Combined with these difficulties over control of the alloy composition, the growth of As-Sb heterojunctions, such as InAs/GaSb, has shown a complex kinetic behavior in forming a specific heterointerface structure. Studies focused on InAs/GaSb superlattices (SL), as well as SL containing As 1Ày Sb y ternaries, indicate that a number of factors can lead to significant grading of the antimony composition across the interface [6][7][8][9][10]. Results from molecular beam epitaxy (MBE) studies of InAs/GaSb and GaAs 1Ày Sb y / GaAs indicate that antimony can segregate during growth forming a surface accumulation or segregation layer.…”

Interface structures of III–V semiconductor heterostructures

“…Cross‐sectional scanning tunneling microscopy (XSTM) has emerged as a powerful technique to characterize III–V semiconductor heterostructures 2, 9–18. Precise characterization of these materials is made possible by the fact that a zinc‐blende III–V crystal readily cleaves along the {110} faces, producing a nearly defect‐free surface that presents a cross‐sectional view through a single lattice plane of structures grown on (001) substrates 9.…”

“…First, the different III–V materials in a heterostructure usually have a different topographic height in filled‐state images. Until the past few years 2, 14–17, discussion of this difference focused on electronic effects, specifically on the band gaps and band alignments (for filled states, the valence band maximum) and the associated number of bands contributing to the tunneling 9–13. The second contrast issue is related to the relative appearance of point defects associated with interdiffusion between the materials.…”

Cross-sectional scanning thermal microscopy of ErAs/GaAs superlattices grown by molecular beam epitaxy

“…In this measurement configuration, we can directly characterize thermal, electronic, and other material properties of interfaces and buried layers in heterostructures using scanned probe microscopy. [22][23][24] In this study, an ErAs/GaAs superlattice structure was employed in our analysis of thermal characteristics since the given structure is a highly promising candidate for thermoelectric devices application [25] because of the semimetallic properties of ErAs embedded in GaAs combined with decreasing thermal conductivity due to the phonon scattering from the ErAs/GaAs nanostructures. [11,15] …”