AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP22
Atomic Structure of InGaAs Surfaces

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: A. Riposan, University of Michigan
Authors: A. Riposan, University of Michigan
J. Mirecki Millunchick, University of Michigan
B.J. Dall, University of Michigan
C.A. Pearson, University of Michigan
B.G. Orr, University of Michigan
Correspondent: Click to Email
The atomic structure of compound semiconductor alloy surfaces is important for heteroepitaxial growth, as it has an impact on the subsequent microstructure of the film. We examined the morphology and surface reconstruction of In@sub x@Ga@sub 1-x@As alloy layers during growth and after annealing. Films of different compositions were grown by molecular beam eptiaxy on GaAs and InP (001) substrates to thicknesses less than the critical thickness for 3D islanding, and examined using in-situ Scanning Tunneling Microscopy (STM). The surface reconstruction of lattice matched In@sub 0.53@Ga@sub 0.47@As/InP alloys is highly disordered; nearly 25% of the surface is covered with a 4x3 reconstruction and 15% with a c(3x4). Models developed based on the STM data suggest that these reconstructions are terminated by both cation and anion dimers. The surface reconstruction during the growth of alloys under compressive misfit strain was 2x3 according to reflection high energy electron diffraction. However, STM shows that the surfaces are covered with a number of differently reconstructed domains. The majority of the surface of In@sub 0.27@Ga@sub 0.73@As/GaAs layers is covered by a disordered c(3x4), while 34% of the surface consists of short segments of @alpha@2(2x4) with in the terrace. The reconstruction of In@sub 0.81@Ga@sub 0.19@As/InP surfaces, which have the same amount of lattice mismatch, consists of @beta@2(2x4) regions resting upon an underlying 4x3. The coverage of the @beta@2(2x4) decreases from 50% to 34% after a 25 minute anneal at the growth conditions. This behavior is consistent with the decrease of the surface In concentration during annealing, suggesting that the @beta@2(2x4) regions on this surface are related to In surface segregation.