  We have previously demonstrated that in the context of two-dimensional (2D)
coherent electronic spectroscopy measured by phase modulation and
phase-sensitive detection, an \emph{incoherent} nonlinear response, due to
pairs of photoexcitations produced via linear excitation pathways, contribute
to the measured signal as unexpected background [Gr\'egoire et al., J.\ Chem.\
Phys. \textbf{147}, 114201 (2017)]. Here, we simulate the effect of such
incoherent population mixing in the photocurrent signal collected from a GaAs
solar cell by acting externally on the transimpedance amplifier circuit used
for phase-sensitive detection, and we identify an effective strategy to
recognize the presence of incoherent population mixing in 2D data. While we
find that incoherent mixing is reflected by cross-talk between the linear
amplitude at the two time-delay variables in the four-pulse excitation
sequence, we do not observe any strict phase correlations between the coherent
and incoherent contributions, as expected from modelling of a simple system.
