An investigation of gallium self-diffusion in GaAs
An investigation of gallium self-diffusion in GaAs
Conflict between previous self-diffusion data coupled with a limited knowledge and understanding of point defects and migration processes in GaAs highlighted the need for further information in this area. The work presented in this thesis first describes basic concepts of point defects and atomic diffusion. A review of diffusion in CaAs is then followed by experimental measurements, obtained by the author, of 72Ga diffusion in CaAs over the temperature range 1025°C to 11000°C, under controlled and monitored conditions of arsenic pressure and final gallium surface concentration. Circles of 72Ca were evaporated onto one face of GaAs wafers ((100)orientation, n-type, Bridgman grown, undoped with a carrier concentration of 2c1016cn 3, mobility of 4270cm2V-1s 1 and an initial etch pit density of about 4000cm 2) which were sealed in pre-baked, evacuated silica ampoules, along with sufficient arsenic to create the required pressure, usually 0.75atm. Surface quality of the wafers was maintained by minimising oxygen and water vapour content in the ampoules, reducing temperature gradients to fl °C and by imposing an arsenic pressure. 72Ga diffusion profiles, after annealing for times up to Mrs, were determined by radio-isotope assay of layers removed from the slices by anodic oxidation followed by oxide dissolution in 202 RCl. Theoretical curves of best fit to experimental diffusion data obtained at a constant arsenic pressure of 0.75atm yielded D ) between 3xl0 15 and 9x10 15~2s 1 over the temperature range 1025°C to 1100°C. D( ) (at PMZO.75atm) can be expressed in the form: D ). 6.3x10 6 expf 2. eV)em2s l. ~TNo specific 72 Ca diffusion mechanism may be inferred from these data alone; however an increase in to 3.Oatm at 1025°C resulted in an ~2 apparent decrease in D(Cb and militates against 72Ga diffusing vianeutral vacancies on the gallium sublattice. The order of magnitude of D(~) obtained was in broad agreement with the extrapolated values of Goldstein, however the activation energy observed was approximately half that reported by Goldstein.
University of Southampton
1980
Palfrey, Helen Deborah
(1980)
An investigation of gallium self-diffusion in GaAs.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Conflict between previous self-diffusion data coupled with a limited knowledge and understanding of point defects and migration processes in GaAs highlighted the need for further information in this area. The work presented in this thesis first describes basic concepts of point defects and atomic diffusion. A review of diffusion in CaAs is then followed by experimental measurements, obtained by the author, of 72Ga diffusion in CaAs over the temperature range 1025°C to 11000°C, under controlled and monitored conditions of arsenic pressure and final gallium surface concentration. Circles of 72Ca were evaporated onto one face of GaAs wafers ((100)orientation, n-type, Bridgman grown, undoped with a carrier concentration of 2c1016cn 3, mobility of 4270cm2V-1s 1 and an initial etch pit density of about 4000cm 2) which were sealed in pre-baked, evacuated silica ampoules, along with sufficient arsenic to create the required pressure, usually 0.75atm. Surface quality of the wafers was maintained by minimising oxygen and water vapour content in the ampoules, reducing temperature gradients to fl °C and by imposing an arsenic pressure. 72Ga diffusion profiles, after annealing for times up to Mrs, were determined by radio-isotope assay of layers removed from the slices by anodic oxidation followed by oxide dissolution in 202 RCl. Theoretical curves of best fit to experimental diffusion data obtained at a constant arsenic pressure of 0.75atm yielded D ) between 3xl0 15 and 9x10 15~2s 1 over the temperature range 1025°C to 1100°C. D( ) (at PMZO.75atm) can be expressed in the form: D ). 6.3x10 6 expf 2. eV)em2s l. ~TNo specific 72 Ca diffusion mechanism may be inferred from these data alone; however an increase in to 3.Oatm at 1025°C resulted in an ~2 apparent decrease in D(Cb and militates against 72Ga diffusing vianeutral vacancies on the gallium sublattice. The order of magnitude of D(~) obtained was in broad agreement with the extrapolated values of Goldstein, however the activation energy observed was approximately half that reported by Goldstein.
This record has no associated files available for download.
More information
Published date: 1980
Identifiers
Local EPrints ID: 459125
URI: http://eprints.soton.ac.uk/id/eprint/459125
PURE UUID: 7468872b-3cad-47ac-8b34-55a62c626cd3
Catalogue record
Date deposited: 04 Jul 2022 17:04
Last modified: 04 Jul 2022 17:04
Export record
Contributors
Author:
Helen Deborah Palfrey
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics