Lattice-mismatched GaAsP Solar Cells Grown on Silicon by OMVPE

We report on lattice-mismatched GaAs
_0.7
P
_0.3
solar cells grown on silicon substrates. This composition of GaAs
_0.7
P
_0.3
has a band gap of about 1.7 eV and is well suited as the top junction of a III-V/Si two-junction tandem solar cell. Using a thin, high-quality GaP nucleation layer, a lattice-matched GaN
_0.02
P
_0.98
buffer layer, and a compositionally graded GaAs
_x
P
_1-x
buffer layer, the threading dislocation densities was reduced to less than 10
⁸
cm
^-2
in the active region. The efficiencies of these single-junction cells without any antireflection coatings were as high has 9.8% under the AM1.5G spectrum. The quality of these solar cells based on V
_oc
is comparable to the best III-V solar cells ever grown on Si substrates with a III-V buffer