INFRARED AND ELECTRICAL CHARACTERIZATION OF MULTILAYERED N-TYPE GAAS WAFERS

We have characterized GaAs epitaxial wafers (N active/N+ buffer/N+ substrate) intended for varactors and mixer diodes. I-V and C-V measurements demonstrated that the active layers were excellent. Transmission-loss measurements suggested that the buffer-layer carrier concentrations were too low and/or the wafers had an additional high-resistivity interface layer. The layer thicknesses were measured using a spherical drilling technique followed by chemical delineation. Analysis of infrared reflectance measurements provided the carrier concentrations of the layers as well as their thicknesses. Both the drilling-delineation measurements and the reflectance measurements confirmed the transmission-loss indications.