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|Title:||Study of Deep Levels in (100) and (311)B Molecular Beam Epitaxial Gallium-Arsenide by Constant-Capacitance Deep Level Transient Spectroscopy|
|Author(s):||DeJule, Ruthanna Yusa|
|Department / Program:||Electrical Engineering|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Engineering, Electronics and Electrical|
|Abstract:||The study of deep level traps in molecular beam epitaxial (MBE) GaAs by constant capacitance deep level transient spectroscopy (CC-DLTS) has been divided into three parts. First, the deep level centers unique to MBE GaAs layers were identified; second, the effect of growth and annealing conditions on trap concentrations were determined; and finally, that information was applied to the study of the nature of the deep level traps in (100) and (311)B GaAs layers.
The first study of deep level traps in (100) MBE GaAs layers took place over ten years ago. As many as nine traps were detected. In subsequent DLTS studies in this laboratory and in various other laboratories, levels labeled M1, M3 and M4 were consistently detected. These levels have become generally associated with (100) MBE GaAs layers.
Optimization of growth parameters has been effective in reducing concentrations of various deep levels in (100) GaAs. The growth of molecular beam epitaxial (MBE) layers using dimeric As as a source material has been shown to reduce electron trap concentrations measured by deep level transient spectroscopy (DLTS) and "defect"-related luminescence. Molecular beam epitaxial layers grown on (311)B oriented substrates with the use of a metallic As source have been studied and only two (M1 and M4) of the three DLTS peaks generally associated with MBE material are detected. Silicon-doped layers have been grown simultaneously on (311)B and (100) substrates. The deep level peak labeled M3 consistently appears in layers grown on (100) substrates but is absent in five out of seven layers grown on (311)B substrates. Photoluminescence (PL) defect bound exciton peaks were weak or absent in the (311)B layers. Variations in carbon incorporation in the layers grown on the two substrate orientations were observed but no correlation could be made to the strengths of the defect lines.
The quality of the epitaxial layers from a deep level point of view was shown to be insignificantly affected by both high dislocation densities and reduced residual impurities due to substrate prebacking. However, trap concentrations were observed to change markedly under various growth parameter settings and annealing conditions. (Abstract shortened with permission of author.)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
|Date Available in IDEALS:||2014-12-15|
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Dissertations and Theses - Electrical and Computer Engineering
Dissertations and Theses in Electrical and Computer Engineering
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois