  Tellurium allows attaining heavy n-type doping levels in GaAs, which is
suited to achieve very low contact resistivities in solar cells. Besides, it
modifies the energy bandgap of MOVPE-grown GaInP by reducing the group-III
sublattice ordering and presents a strong memory effect which induces residual
n-type doping in subsequent layers, potentially detrimental to the performance
of the solar cell. In this work, we present an inverted rear-heterojunction
GaInP solar cell that employs a thick Te-doped GaInP layer as absorber, with a
doping profile obtained exclusively by controlling the memory effect of Te
coming from the preceding growth of a heavily doped GaAs contact layer. In this
way, GaInP is partially disordered with the use of no additional surfactant,
leading to an increase in the solar cell bandgap of around 35 meV as compared
to traditional samples doped with silicon. In the proof-of-concept experimental
devices developed so far, the use of a rear-heterojunction configuration and
the bandgap increase results in a global open-circuit voltage enhancement of
109 mV. The photocurrent decreases by 1.32 mA/cm2, mostly due to the bandgap
blue-shift, with about 0.35 mA/cm2 attributable to lower carrier collection
efficiencies. These preliminary results are discussed by analyzing the I-V
curve parameters and quantum efficiencies of a Te-doped rear-heterojunction, a
Si-doped rear-heterojunction and a Si-doped front-junction solar cell. An
additional advantage is that the emitter sheet resistance is reduced from 551
to 147 ohms/sq, which offers potential for higher efficiencies through lower
front grid shadowing factors, as demonstrated with the concentrator
measurements presented.
