Species intermixing and phase transitions on the reconstructed (001) surfaces of GaAs and InAs

Scanning tunneling microscopy has been used to study the transition in surface structure between the As-terminated 2×4 and c(4×4) reconstructions on both GaAs(001) and InAs(001), as a function of surface temperature under an ${\mathrm{As}}_2$ flux. For both materials, two-phase surface reconstructions exist through the transition regime. On GaAs, the two-phase surface consists of disordered (2×4)-like structures plus a c(4×4)-like phase terminating one monolayer below the 2×4 surface. On InAs, a disordered asymmetric 1×3 phase occurs {a(1×3)} in addition to the main phases, one monolayer below each main phase. In both cases, simple addition of As via As-on-As chemisorption cannot account for the formation of the c(4×4) reconstruction from the 2×4 surface. The c(4×4) phase is inherently multilayered, which explains how the structure can form without the addition or removal of the group III component and still maintain its layering registry with the residual 2×4 or a(1×3) phase. One result of this formation process is the necessary intermixing of group III and group V species in the second layer of the c(4×4) reconstruction. Direct evidence of species intermixing on the top layer of the InAs(001)-a(1×3) structure is also shown and models for all of these reconstructions are proposed.