New concept of lateral GaAs field emitter for sensor applications

We present a novel lateral field emitter structure for sensing applications , which is based on GaAs. According to the Fowler-Nordheim theory, the emit ted current depends exponentially on the distance between the cathode and t he anode. Hence, this effect is predestined for sensing of vibration,: acce leration, and pressure. We have designed and fabricated a lateral field emi tter structure consisting of two wedges vis-a-vis. They are etched anisotro pically in n(+) -doped epitaxial GaAs. One of the wedges-is released by fro nt side bulk micromachining to form a flexible cantilever. This cantilever contains the seismic mass of the accelerometer. The sensing principle is ba sed on the following effect. The electrical field strength at the cathode i s already very strong at relatively low cathode-anode voltages due to the g eometrical parameters: (i) the low radius of the emission wedge, its:radius of curvature is much smaller than 50 nm and (ii) very small distance betwe en the cathode and the anode. Acceleration or vibration causes the cantilev er to bend, so that the distance between the two wedges varies accordingly. This causes a modulation of the electrical field strength at the cathode a nd leads to a modulation of the emission current. The proposed sensor has t he advantage of high sensitivity combined with a good temperature insensiti vity. Classical beam theory was applied to define the geometrical parameter s and the corresponding deflection of the cantilever. (C) 1999 American Vac uum Society. [S0734-211X(99)08502-9].