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/10.2172/6633607· OSTI ID:6633607

Paul, W.

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)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 6633607
• Report Number(s): NREL/TP-411-5457; ON: DE93010021
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
GERMANIUM ALLOYS
CHEMICAL VAPOR DEPOSITION
SILICON ALLOYS
SILICON SOLAR CELLS
FABRICATION
AMORPHOUS STATE
ELECTRICAL PROPERTIES
GLOW DISCHARGES
INTERMETALLIC COMPOUNDS
MICROSTRUCTURE
PROGRESS REPORT
SILICON
ALLOYS
CHEMICAL COATING
CRYSTAL STRUCTURE
DEPOSITION
DIRECT ENERGY CONVERTERS
DOCUMENT TYPES
ELECTRIC DISCHARGES
ELEMENTS
EQUIPMENT
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SEMIMETALS
SOLAR CELLS
SOLAR EQUIPMENT
SURFACE COATING
photovoltaics
solar cells
amorphous silicon
electronic
alloys
140501* - Solar Energy Conversion- Photovoltaic Conversion
360101 - Metals & Alloys- Preparation & Fabrication
360104 - Metals & Alloys- Physical Properties