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Title:Growth and Characterization of Carbon-Doped Aluminum(x) Gallium(1-X) Arsenide and Aluminum(x) Gallium(1-X) Phosphide
Author(s):Hofler, Gloria Emilia
Doctoral Committee Chair(s):Hsieh, K.C.
Department / Program:Electrical Engineering
Discipline:Electrical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Physics, Condensed Matter
Abstract:Carbon-doped GaAs and Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As with carbon concentrations ranging from 2 $\times$ 10$\sp $ cm$\sp{-3}$ to 3 $\times$ 10$\sp{20}$ cm$\sp{-3}$ have been characterized with Hall effect measurements, secondary ion mass spectrometry (SIMS), double crystal x-ray diffraction and nuclear reaction analysis in an ion channeling geometry. It was revealed that the surface morphology and elemental composition of p$\sp+$ Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As were critically dependent on the growth conditions due to the existence of a chemical reaction (etching) with the byproducts of the CCl$\sb4$ source. This "etching" effect was also observed during the growth of p-type Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$P by MOCVD using CCl$\sb4$ as the dopant source. The hole concentration obtained from MOCVD grown Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$P using CCl$\sb4$ is at least an order of magnitude lower than the reported concentrations in films grown by MOMBE.
Carbon-doped epilayers grown by MOCVD yielded abrupt dopant profiles. However, the redistribution of carbon was observed during the growth of GaAs structures by MOMBE. This may result from defects generated due to the specific MOMBE growth conditions and was not observed in n-i-p+-i-n or HBT structures grown by MOCVD.
The doping efficiency of carbon in Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As is shown to decrease when (C) $\ge$ 10$\sp $ cm$\sp{-3}.$ Two mechanisms are responsible: (1) the passivation of carbon acceptors by hydrogen and (2) the incorporation of electrically neutral carbon precipitates or interstitial clusters. For a single p$\sp+$ Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As layer, the hydrogenation of carbon acceptors can be reversed by a rapid thermal anneal step below 500$\sp\circ$C. However, sample annealing at higher temperatures causes a reduction in hole concentration with a parallel drop in the lattice mismatch between the epitaxial layers and the GaAs substrate.
The decrease in the lattice mismatch and the degradation of hole conduction upon high-temperature annealing are shown to result from the presence of interstitial carbon or carbon precipitates. These findings were confirmed by a direct measurement of the lattice site location of carbon atoms in GaAs and Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As both as-grown and annealed under rapid thermal annealing and arsenic rich conditions.
Issue Date:1993
Description:140 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.
Other Identifier(s):(UMI)AAI9329058
Date Available in IDEALS:2014-12-16
Date Deposited:1993

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