Dielectrics on Gallium Arsenide Using Silicon as a Sacrificial Layer: Formation Kinetics and Interface State Densities
Wang, Zhonghui Alex
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https://hdl.handle.net/2142/82915
Description
Title
Dielectrics on Gallium Arsenide Using Silicon as a Sacrificial Layer: Formation Kinetics and Interface State Densities
Author(s)
Wang, Zhonghui Alex
Issue Date
1998
Doctoral Committee Chair(s)
Rockett, Angus A.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Language
eng
Abstract
Interface properties were studied and reaction kinetics characterized in a dielectric/Si/GaAs structure formed by direct nitridation or UV ozone oxidation of a sacrificial pseudomorphic epitaxial Si layer on a GaAs (100) substrate. The nitridation and oxidation process kinetics were studied by X-ray photoelectron spectroscopy (XPS). Thicknesses and compositions were obtained through the quantitative relationships among the relative intensities of different core-level peaks and secondary electron take-off angles in X-ray photoelectron spectra. The nitride thickness was logarithmic with time with formation of ∼14 A near stoichiometric Si3N4 in 10 s. Oxygen contamination of the nitride increased with time probably due to the reaction with oxygen sputtered from the quartz window in the ECR nitridation system. Excess nitridation resulted in As out-diffusion and damage to the GaAs/Si interface. Near ideal C-V curves and low interface trap densities at ∼3 x 1011 eV-1cm-2 were found in a sample with 25 A of initial Si nitrided for 15 minutes. High resolution transition electron microscopy demonstrated a smooth abrupt Si3N4/(Si)GaAs interface and formation of a high quality of Si3N4 layer. Similar studies of oxidation of the Si layer were made. Oxidation is logarithmic with time as for nitridation. A 10 A Si layer developed surface roughness upon oxidation. Interface state densities in some oxidized samples were near the best ever obtained in Si oxide /GaAs interfaces, ∼1012--10 14 ev-1 cm-2, but were still significantly greater than the nitride result. Both Ga and As out-diffusion through Si/SiO2 layers were observed in XPS profiles during heat treatment of the structure. The Ga diffusion activation energy was 1.55 eV at low temperature and low concentration. The thickness of the residual Si ICL has no effect on Dit for initial Si thickness >10A.
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