Dopant diffusion and segregation in semiconductor heterostructures: Part III, diffusion of Si into GaAs |
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Authors: | C-H Chen UM Gösele TY Tan |
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Institution: | (1) Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708-0300, USA (E-mail: ttan@acpub.dduke.edu), US |
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Abstract: | We have mentioned previously that in the third part of the present series of papers, a variety of n-doping associated phenomena
will be treated. Instead, we have decided that this paper, in which the subject treated is diffusion of Si into GaAs, shall
be the third paper of the series. This choice is arrived at because this subject is a most relevent heterostructure problem,
and also because of space and timing considerations. The main n-type dopant Si in GaAs is amphoteric which may be incorporated
as shallow donor species SiGa
+ and as shallow acceptor species SiAs
-. The solubility of SiAs
- is much lower than that of SiGa
+ except at very high Si concentration levels. Hence, a severe electrical self-compensation occurs at very high Si concentrations.
In this study we have modeled the Si distribution process in GaAs by assuming that the diffusing species is SiGa
+ which will convert into SiAs
- in accordance with their solubilities and that the point defect species governing the diffusion of SiGa
+ are triply-negatively-charged Ga vacancies VGa
3-. The outstanding features of the Si indiffusion profiles near the Si/GaAs interface have been quantitatively explained for
the first time. Deposited on the GaAs crystal surface, the Si source material is a polycrystalline Si layer which may be undoped
or n+-doped using As or P. Without the use of an As vapor phase in the ambient, the As- and P-doped source materials effectively
render the GaAs crystals into an As-rich composition, which leads to a much more efficient Si indiffusion process than for
the case of using undoped source materials which maintains the GaAs crystals in a relatively As-poor condition. The source
material and the GaAs crystal together form a heterostructure with its junction influencing the electron distribution in the
region, which, in turn, affects the Si indiffusion process prominently.
Received: 19 April 1999 / Accepted: 3 May 1999 / Published online: 4 August 1999 |
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Keywords: | PACS: 61 72Vv 61 72Ss 61 72Yx |
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