Thermal degradation mechanisms in GaAs solar cells with high-temperature contacts

Conference · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6707027

Tobin, S P; Bajgar, C; Vernon, S M; Keavney, C J; Chung, M A; Ruby, D S

This objective of this work was to characterize the thermal stability of GaAs solar cells with high-temperature contacts. High-temperature stability is important for threat environments in space, for compatibility with high-temperature assembly techniques, and for enhanced reliability of cells. Our contact system, described previously, relies on a Pt solid-phase ohmic contact, a TiN barrier layer, and an Au conductor, with contact to a heavily doped p-GaAs contact layer. The behavior of both flat-plate and concentrator cells has been characterized as a function of temperature (400-600/degree/C) and time (5-15 minutes) of the anneal. We find that GaAs cells experience minimal electrical degradation up to 550/degree/C for 5 minutes, or to 490/degree/C for 15 minutes. Increases in the 2kT perimeter dark current are responsible for small decreases in Voc and FF up to these temperatures. At higher temperatures a drastic decrease in efficiency is caused by metallurgical reactions at isolated regions along the grid lines. The reaction, which appears to involve Au-Ga, is initiated at the edges of the grid lines. Away from edges, the contacts are metallurgically stable to at least 600/degree/C. 4 refs., 8 figs., 4 tabs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA); Spire Corp., Bedford, MA (USA); Air Force Wright Aeronautical Labs., Wright-Patterson AFB, OH (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6707027
• Report Number(s): SAND-88-2498C; CONF-880965-20; ON: DE89001375
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
ANNEALING
DATA
DIRECT ENERGY CONVERTERS
EFFICIENCY
ELECTRIC CONTACTS
ELECTRICAL EQUIPMENT
ELEMENTS
EQUIPMENT
GALLIUM ARSENIDE SOLAR CELLS
GOLD
HEAT TREATMENTS
INFORMATION
METALS
NUMERICAL DATA
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
SOLAR CELLS
SOLAR EQUIPMENT
STABILITY
THERMAL DEGRADATION
TRANSITION ELEMENTS