Ever though III–V solar cells have demonstrated superior performance,
but production of low cost high efficiency III–V solar
cells is still challenge due to expensive materials cost including
Au-based and Ag-based contact metallurgy. Substituting costly
Au-based or Ag-based contacts and interconnects with low-cost
Cu-based systems are being considered. However, the Cu-based
contacts to III–V material face severe issue of rapid Cu diffusion
into the material and formation of deep acceptor levels [1–3].
In our previous study, we proposed an approach for Cu-based
contacts on GaAs and Ge substrate [4,5]. By using a diffusion barrier
at the bottom of the device and a passivation layer at the top
to prevent diffusion and oxidation, we can fabricate the ohmic contacts
with specific contact resistances in the range of 106 O cm2.
However, reliability of such contacts and the solar cells using these
contacts need to be established as it is extremely important for
practical applications.
We report here the electrical and thermal stability of the n-type
and p-type Cu-based contacts after subjecting them to periodic
heat treatment and high current stress process. Furthermore, the
reliability of III–V concentration solar cells adopting these low contacts
is demonstrated to show their practicability.