Measurement of high electron drift velocity in a submicron, heavily doped graded gap Al<i>x</i>Ga1−<i>x</i>As layer

Abstract

We have directly determined a high velocity (v=2×107 cm/s) for electrons in a submicron (0.42 μm), strongly graded (quasifield F=8.8 kV/cm) highly doped ( p=4×1018 cm−3) AlxGa1−xAs layer. A transit time of only 1.7 ps was measured (an order of magnitude shorter than that for F=1.2 kV/cm). Such a structure would be ideal for the low resistance base of a high-speed n-p-n transistor.