Preparation of silicon substrates for gallium-arsenide solar cells by electron-beam-pulse processing. Annual technical report, March 15, 1980-March 15, 1981

Technical Report · Fri May 01 00:00:00 EDT 1981

DOI:https://doi.org/10.2172/5357745· OSTI ID:5357745

Tobin, S. P.

In the past year a process has been developed for creating high-quality epitaxial layers of germanium on silicon substrates using rapid heating and cooling with a pulsed electron beam. This single-crystal germanium coating is the key to the production of high efficiency GaAs solar cells on low-cost silicon substrates in an economical manner. Thin (less than or equal to 1 ..mu..m) layers of Ge have been deposited on Si wafers by chemical vapor deposition (CVD) in single-crystal form or by vacuum evaporation in amorphous or polycrystalline form. The CVD films have given the best results, with good crystallinity and electrical properties as deposited. A persistent problem with surface roughness in the as-deposited films has been overcome by pulsed electron beam melting of the near-surface region in time periods on the order of a microsecond. The brief molten period smooths the surface features without compromising the crystallinity, electrical properties, or interfacial abruptness of the Ge film. These layers are of a quality suitable for further evaluation by GaAs growth and cell processing in the next phase of the program. Pulsed electron beam processing also serves a vital function for the evaporated Ge films, which are melted by the beam and recrystallized on the Si substrates, epitaxial single crystal Ge layers result from amorphous or polycrystalline starting films. To date results have not been as satisfactory as for CVD films; contamination from several sources has been identified as a problem. Many of these sources have been eliminated, so that a decision on the intrinsic limitations of the evaporated film approach should be made in the near future.

• Research Organization: Solar Energy Research Inst. (SERI), Golden, CO (United States); Spire Corp., Bedford, MA (USA)
• DOE Contract Number: AC02-77CH00178
• OSTI ID: 5357745
• Report Number(s): DOE/SERI-90021/4; ON: DE82010997
• Resource Relation: Other Information: Portions of document are illegible
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
GERMANIUM
CHEMICAL VAPOR DEPOSITION
ELECTRON BEAM MELTING
ENERGY BEAM DEPOSITION
VACUUM EVAPORATION
AMORPHOUS STATE
CONTAMINATION
ELECTRICAL PROPERTIES
EPITAXY
FILMS
HETEROJUNCTIONS
ION IMPLANTATION
MONOCRYSTALS
POLYCRYSTALS
ROUGHNESS
SILICON
SUBSTRATES
CHEMICAL COATING
CRYSTALS
DEPOSITION
ELEMENTS
EVAPORATION
JUNCTIONS
MELTING
METALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SEMICONDUCTOR JUNCTIONS
SEMIMETALS
SURFACE COATING
SURFACE PROPERTIES
140501* - Solar Energy Conversion- Photovoltaic Conversion