Microstructural studies of epitaxial Ge films grown on (100) GaAs by laser photochemical vapor deposition
Ge films grown on (100) GaAs by laser photochemical vapor deposition (LPVD) in parallel geometry at temperatures (T/sub s/) ranging from /similar to/240 to 415 /sup 0/C have been examined by transmission electron microscopy. For 285 less than or equal toT/sub s/approx. <330 /sup 0/C, a thin (250--700 A) epitaxial film is grown initially but a switch to amorphous material is subsequently observed. At higher substrate temperatures (T/sub s/ approx. >400 /sup 0/C), thicker (approx. >800 A) epitaxial Ge films are grown before the transition to polycrystalline material takes place. In the absence of external 193-nm laser radiation (i.e., growing by conventional low-pressure chemical vapor deposition), the Ge films are completely amorphous (285 less than or equal toT/sub s/less than or equal to330 /sup 0/C) or heavily defected polycrystalline (T/sub s//similar to/400 /sup 0/C). The >100 /sup 0/C temperature reduction for the growth of epi Ge films made possible by LPVD is attributed to the direct production of a species (GeH/sub 3/) by the laser which is collisionally converted to Ge/sub 2/H/sub 6/ en route to the substrate. Upon reaching the (100) GaAs surface, the digermane is pyrolyzed. Experiments with (100) substrates tilted 3/sup 0/ toward (110) yielded thinner (/similar to/120 A), but smooth, epitaxial films which is attributed to the higher density of available nucleation sites. Films grown at 280--330 /sup 0/C on (111) oriented GaAs were completely amorphous which appears to arise from reduced adatom mobilities on (111) surfaces.
- Research Organization:
- University of Illinois, Urbana, Illinois 61801
- OSTI ID:
- 6406998
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 65:10
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GALLIUM ARSENIDES
SORPTIVE PROPERTIES
GERMANIUM
CHEMICAL VAPOR DEPOSITION
MICROSTRUCTURE
AMORPHOUS STATE
EPITAXY
HIGH TEMPERATURE
LASER RADIATION
MONOCRYSTALS
PHOTOCHEMISTRY
POLYCRYSTALS
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY
ARSENIC COMPOUNDS
ARSENIDES
CHEMICAL COATING
CHEMISTRY
CRYSTAL STRUCTURE
CRYSTALS
DEPOSITION
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
ELEMENTS
FILMS
GALLIUM COMPOUNDS
METALS
MICROSCOPY
PNICTIDES
RADIATIONS
SURFACE COATING
SURFACE PROPERTIES
360601* - Other Materials- Preparation & Manufacture
360602 - Other Materials- Structure & Phase Studies