These metallization structures had an
optimal specific contact resistance in the range of 106 X cm2.
Thermal and electrical stress tests showed that the contacts
remained stable after subjected to extreme conditions. The Auger
analysis results showed no significant evidence of diffusion of Cu
atoms into the GaAs layer or Ge substrates. In addition, concentrator
solar cells were fabricated with these metal structures to verify
the applicability of Cu-based contacts for the III–V solar cells. The
solar cell fabricated achieved an efficiency of approximately 30%
at 120 suns. After a thicker (5 lm) cap layer of Cu was implemented,
the conversion efficiency of the Cu-metallized solar cells
improved to 37% at 120 suns. In summary, reliability of the III–V
solar cell with Cu based contacts is demonstrated in this paper.
The reduction in cost achieved by avoiding Au or Ag as demonstrated
has the potential to increase the competitiveness of the
III–V solar cells in the commercial market.