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Lyding, Joseph W. Skala, Stephen Lawrence 2011-05-07T12:43:02Z 2011-05-07T12:43:02Z 10000-01-01 1994 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. Made available in DSpace on 2011-05-07T12:43:02Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9416435.pdf: 3121955 bytes, checksum: f7c57282442dd54bdb353d5246e9ec28 (MD5) Previous issue date: 1994 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:44:46Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:19:45-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9416435 (UMI)AAI9416435 http://hdl.handle.net/2142/20570 eng Copyright 1994 Skala, Stephen Lawrence Physics, Condensed Matter Engineering, Materials Science Scanning tunneling microscopy of III-V semiconductors text Electrical and Computer Engineering Electrical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.