Abstract: A GaAs substrate is reduced to a thickness of no more than 30 &mgr;m, preferably no more than 10 &mgr;m, by grinding. The substrate thus has the characteristics of a film, which prevents breakage of the substrate. A metallization can be provided on the rear of the substrate. The thermal characteristics are improved, because the heat can be transferred to the rear side of the substrate more effectively. Because of the smaller dimensions and good heat dissipation, smaller housings can be utilized. Extremely small holes (micro via holes) are etched into the substrate and provided with via hole fillers.

Abstract: A novel unipolar transistor device has been realized starting from two-dimensional electron systems (2DES) in modulation-doped AlGaAS/GaAs heterostructures. A 600 nm wide 1D channel is insulated laterally from 2DES regimes by 700 nm wide deep mesa etched trenches. The conductivity in the quasi-one-dimensional channel can be tuned via the in-plane lateral-field effect of the adjacent 2DES-gates where the vacuum (or air) in the etched trenches serves as the dielectric. Room temperature operation is demonstrated yielding a 161S transconductance corresponding to 160 mS/mm 2D transconductance.