  We propose and experimentally verify two methods to scale arbitrary units to
photocurrent spectral density (A/eV) in Fourier Transform Photocurrent (FTPC)
spectroscopy. We also propose the FTPC scaling to responsivity (A/W), provided
a narrow-band optical power measurement is available. The constant background
of the interferogram provides a precise determination of the photocurrent
spectral density. The second method relies on the scaled amplitude of the
interferogram. Although the latter method leads to more significant errors, it
still provides good order of magnitude estimates of the total photocurrent. We
demonstrate the technique on a calibrated InGaAs diode and weak responsivity
SiC interdigital sensors. We identify a series of impurity-band and interband
transitions in the SiC sensors.
