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Title:Scanning tunneling microscopy of III-V semiconductors
Author(s):Skala, Stephen Lawrence
Doctoral Committee Chair(s):Lyding, Joseph W.
Department / Program:Electrical and Computer Engineering
Discipline:Electrical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Physics, Condensed Matter
Engineering, Materials Science
Abstract:Scanning tunneling microscopy (STM) has been used to study the (100) surface of GaAs and the (110) plane of cross-sectioned GaAs/AlGaAs heterolayers. Observation of the GaAs(100) surface with STM has characterized the c(8x2) reconstruction and shows that the c(8x2) consists of ordered (4x2) subunits. Each (4x2) subunit contains two As and two Ga dimers, contrary to previous descriptions which include only Ga dimers. This model of the c(8x2) reconstruction also agrees well with results from other experimental techniques. The (2x6) reconstruction is observed to be considerably more complex than the c(8x2) and bears little resemblance to either the c(2x8) or c(8x2) reconstructions.
STM investigations on vicinal GaAs(100) substrates have clearly shown that steps migrate to form arrays of terraces $\sim$175 A wide separated by regions of bunched steps on 2$\sp{\rm o}$ toward (110) oriented substrates after annealing to a temperature high enough to form a mixed c(8x2) and (2x6) reconstruction. The coexistence of the two reconstructions is critical to step bunching as the c(8x2) is observed to occupy only the terraces while the (2x6) exists predominately across the steps. Bunched step arrays are not observed on 2$\sp{\rm o}$ toward (110) oriented substrates, and a considerably higher ratio of (2x6) reconstructions is present on these substrates than on the 2$\sp{\rm o}$ toward (110) oriented substrates.
STM results on cross-sectioned GaAs/AlGaAs heterolayers show differences in current contrast between p- and n-type layers which can be explained by band bending caused by charged oxygen adsorbates on AlGaAs.
Issue Date:1994
Rights Information:Copyright 1994 Skala, Stephen Lawrence
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9416435
OCLC Identifier:(UMI)AAI9416435

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