Growth and Characterization of In(1-x)Ga(x)As(y)P(1-y) and GaAs Using Molecular Beam Epitaxy PDF Download
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Author: D. W. Covington Publisher: ISBN: Category : Languages : en Pages : 129
Book Description
This report describes the technical work accomplished during the first year of a two-year study of binary and quaternary semiconductors grown by molecular beam epitaxy. Research on GaAs materials demonstrated doping profiles for peeled film, mixer diodes and low-high-low, millimeter wave IMPATT diodes. Iron has been investigated as a potential MBE dopant for FET buffer layer applications. Although compensated layers exhibiting the Fe(2+) line at 0.371 eV were obtained for doping oven temperatures less than but close to 1013 C at GaAs growth rates of 1.0 micron per hr. there was unintentional accumulation of iron at the outer surface reserved for the active layer in conventional FET structures. Before initiating the study of quaternary materials, the MBE growth conditions were established for the ternary In(x)Ga(1-x)As. Layers of the latter semiconductor grown on GaAs substrates held at 510 C showed significant changes in surface morphology and electrical properties for x greater than but close to 0.3. A cryopumped MBE system containing six oven positions has been developed for growing the quaternary In(1-x)Ga(x)As(y)P(1-y) which requires relatively intense beams of P molecules. Lattice-matched In(1-x)Ga(x)As(y)P(1-y) layers have been deposited in this system on (001) GaAs substrates using ovens loaded with Ga, In, As, and GaP. Epitaxy was achieved.
Author: D. W. Covington Publisher: ISBN: Category : Languages : en Pages : 129
Book Description
This report describes the technical work accomplished during the first year of a two-year study of binary and quaternary semiconductors grown by molecular beam epitaxy. Research on GaAs materials demonstrated doping profiles for peeled film, mixer diodes and low-high-low, millimeter wave IMPATT diodes. Iron has been investigated as a potential MBE dopant for FET buffer layer applications. Although compensated layers exhibiting the Fe(2+) line at 0.371 eV were obtained for doping oven temperatures less than but close to 1013 C at GaAs growth rates of 1.0 micron per hr. there was unintentional accumulation of iron at the outer surface reserved for the active layer in conventional FET structures. Before initiating the study of quaternary materials, the MBE growth conditions were established for the ternary In(x)Ga(1-x)As. Layers of the latter semiconductor grown on GaAs substrates held at 510 C showed significant changes in surface morphology and electrical properties for x greater than but close to 0.3. A cryopumped MBE system containing six oven positions has been developed for growing the quaternary In(1-x)Ga(x)As(y)P(1-y) which requires relatively intense beams of P molecules. Lattice-matched In(1-x)Ga(x)As(y)P(1-y) layers have been deposited in this system on (001) GaAs substrates using ovens loaded with Ga, In, As, and GaP. Epitaxy was achieved.
Author: Mahsa Mahtab Publisher: ISBN: Category : Languages : en Pages :
Book Description
GaAs(1-x)Bi(x) (x = 0 to 17%) optical properties were investigated by spectroscopic ellipsometry (in energy ranges of 0.37-9.0 eV). Optical features in the dielectric function, known as the critical points, were distinguished and modeled using standard analytic line shapes. The energy dependence of the critical points energies was thoroughly investigated as a function of Bi content and thin film strain. Critical points analysis in the Brillion zone showed that the top of the valence band is most strongly dependent on Bi content compared to other parts of the band structure. In addition, an interesting new critical point was observed that is attributed to alternative allowed optical transitions made possible by changes to the top of the valence band caused by resonant interactions with Bi orbitals. Several of the critical points were extrapolated to 100% Bi and showed reasonable agreement with the calculated band structure of GaBi. GaAs(1-x)Bi(x) (x= 03, 0.7 and 1.1%) based p+/n and n+/p heterostructure photovoltaic performance was characterized through IV and CV measurement. By introduction of Bi into GaAs, a non-zero EQE below the GaAs band edge energy was observed while the highest efficiency was obtained by ~ 0.7% Bi incorporation. EQE spectrum was modeled to find the minority carrier diffusion lengths of ~ Ln = 1600 and Lp = 140 nm for p-doped and n-doped GaAs92Bi08 in the doping profile of 10^15 - 10^16 cm^-3. Analysis of the CV measurement confirmed the background n-doping effect of Bi atom and the essential role of the cap layer to reduce multi-level recombination mechanisms at the cell edge to improve ideality factor. Low temperature grown GaAs was optimized to be used as photoconductive antenna in THz time-domain spectroscopy setup. The As content was investigated to optimize photo-carrier generation using 1550 nm laser excitation while maintaining high mobility and resistivity required for optical switching. A barrier layer of AlAs was added below the LT-GaAs to limit carrier diffusion into the GaAs substrate. Moreover, LT-GaAs layer thickness and post-growth annealing condition was optimized. The optimized structure (2-μm LT-GaAs on 60-nm AlAs, under As2:Ga BEP of ~7, annealed at 550°C for 1 minute) outperformed a commercial InGaAs antenna by a factor of 15 with 4.5 THz bandwidth and 75 dB signal-to-noise ratio at 1550 nm wavelength.
Author: D. W. Covington
Author: D. W. Covington![Growth and Characterization of In [subscript 1-x] Ga [subscript X] As [subscript Y] P [subscript 1-y] AndGaAs Using Molecular Beam Epitaxy PDF](https://books.google.com/books/content/images/frontcover/DXmAkgAACAAJ?fife=w80-h100)
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