FAR-INFRARED MEASUREMENTS OF THE MOBILITY AND CARRIER CONCENTRATION IN LIGHTLY DOPED GAAS ON SI(100)

GaAs layers with thicknesses from 1 to 8-mu-m were grown by molecular-beam epitaxy onto Si(100) substrates. These epitaxial layers were lightly doped with Si (N(D) congruent-to 2 X 10(16) cm-3). The determination of accurate numbers for the carrier concentrations and mobilities in the GaAs is complicated by the low doping and the dimensions of the films. However, a new approach in IR spectroscopy that combines a conventional reflectance measurement from 50 to 500 cm-1 with a transmittance measurement in the very far-infrared range from 12 to 62 cm-1 is demonstrated to provide precise information on both carrier concentrations and mobilities. A comparison of the results obtained at room temperature from IR and Hall measurements reveals that the nondestructive IR technique is an easy to perform and excellent characterization tool for the Ga As layers.