In this paper we report results of magnetooptical measurements done on standard InAs MOCVD layers grown on GaAs. Extremely narrow lines (half-widths of the order of 20 mT) -narrower than found by other authors in high quality MBE InAs epilayers on GaAs -as well as the lines of typical half-widths have been found both in the photoconductivity spectra and in the transmission spectra. A detailed comparison with the theoretical dependence of shallow donor and Landau level energies on magnetic field

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... leads to the conclusion that they originate from cyclotron resonance and impurity-shifted cyclotron resonance transitions in that material.