Structural and electronic studies of a-SiGe:H alloys. Final subcontract report, 1 January 1991--28 February 1993

Technical Report · Thu Apr 01 00:00:00 EST 1993

DOI:https://doi.org/10.2172/10151531· OSTI ID:10151531

Paul, W ^[1]

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1. Harvard Univ., Cambridge, MA (United States)

This report describes work to produce alloys of a-Si{sub 1-x}Ge{sub x}:H of improved photoelectronic quality by plasma-enhanced chemical vapor deposition (PECVD). The goal was to discover optimum preparation conditions for the end-component, a-Ge:H, to establish whether modification of the usual practice of starting from a-Si:H preparation conditions was advisable. Such modification, found to be necessary, gave films of a-Ge:H with efficiency-mobility-lifetime products ({eta}{mu}{tau}) 10{sup 2} to 10{sup 3} higher than were earlier available, in homogeneous environmentally stable material. Both a-Ge:H and a-Si{sub 1-x}Ge{sub x}:H of large x were studied in detail. Alloy material was shown to have {eta}{mu}{tau} 10{sup 2} larger than found earlier. However, just as the {eta}{mu}{tau} of a-Si:H decreases when Ge is added, so also the {eta}{mu}{tau} of these alloys with Si addition. By contrast, the ambipolar diffusion lengths, L{sub o} which are governed by the hole mobility, vary by only a factor of two over the whole alloy series. Using the experimental finding of a small valence band offset between a-Si:H and a-Ge:H compositional fluctuations on a 10-mm scale are suggested to explain the behavior of {eta}{mu}{tau} and L{sub o} The implications for eventual improvement of the alloys are profound, but require direct experimental tests of the postulated compositional fluctuations.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States); Harvard Univ., Cambridge, MA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-83CH10093
• OSTI ID: 10151531
• Report Number(s): NREL/TP-411-5457; ON: DE93010021
• Resource Relation: Other Information: PBD: Apr 1993
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
SILICON SOLAR CELLS
FABRICATION
SILICON ALLOYS
CHEMICAL VAPOR DEPOSITION
GERMANIUM ALLOYS
PROGRESS REPORT
SILICON
AMORPHOUS STATE
INTERMETALLIC COMPOUNDS
GLOW DISCHARGES
MICROSTRUCTURE
ELECTRICAL PROPERTIES
140501
360101
360104
PHOTOVOLTAIC CONVERSION
PREPARATION AND FABRICATION
PHYSICAL PROPERTIES