Mapping the effective mass of electrons in III-V semiconductor quantum confined structures

The electron effective mass m(e)(*) can be calculated from the Kramers-Kronig transformation of electron energy loss spectra (EELS) for III-V semiconductor materials. The mapping capabilities of a scanning transmission electron microscope, equipped with a Gatan Enfina((TM)) EELS system are exploited to produce maps showing the variation of m(e)(*) with nanometer scale resolution for a range of semiconductors. The analysis was carried out on three material systems: a GaInNAs quantum well in a GaAs matrix; InAs quantum dots in a GaAs matrix, and bulk wurzitic GaN. Values of m(e)(*) were measured as similar to 0.07m(0) for GaAs and 0.183m(0) for GaN, both in excellent agreement with the literature. It has also been shown that the high frequency dielectric constant can be calculated using the Kramers-Kronig methodology. When the high frequency dielectric constant is incorporated into the calculations a much more accurate visual representation of m(e)(*) is displayed in the maps.