Explicit evidence of collision broadening for impurity cyclotron resonance spectrum by photoexcited carriers in n-GaAs

First systematic observation of the collision broadening caused by photoexcited carriers for impurity cyclotron resonance (ICR) spectra in semiconductors has been performed with respect to hydrogenic donors in high purity n-GaAs grown by MBE. So far studies on the line-broadening of the ICR have been only focused on the lifetime broadening of energy levels involved in the resonance, for example, the phonon broadening, and the inhomogeneous broadening as the Stark or concentration broadenings, We have measured full width at half maximum (FWHM) of the ICR for the 1s --> 2p(+1) transition on donor impurities. The FWHM of the ICR has been presented as functions of the electron density and the magnetic field. We have discussed experimental results on the FWFM of the ICR in light of the electron-neutral donor scattering in the presence of a magnetic field.