Infrared reflection and transmission of undoped and Si-doped InAs grown on GaAs by molecular beam epitaxy

Abstract

Nondestructive optical methods, based on measurements of the 'plasma edge' and the Moss-Burstein shift, are investigated as contactless alternatives to Hall measurements for determining carrier concentrations. Infrared reflection and transmission spectra of undoped and Si-doped InAs grown on GaAs by MBE are studied. A curve-fitting procedure is developed to fit the reflectivity spectra with or without phonon-plasmon coupling. The range of carrier concentrations over which these optical methods can provide useful characterization is evaluated. The effective mass determined from 'plasma edge' measurements agrees well with the simple Kane model for n below 2.7*1019 cm-3. For n above 4*1019 cm-3, the sample effective mass deviates considerably from the simple Kane model. Excitonic structure in the absorption edge is reported for high-purity undoped samples.