DOPING PROFILES FOR INDIUM-ANTIMONIDE MAGNETORESISTORS

Indium antimonide is of interest for magnetoresistors in position- and speed-sensing applications. These sensors are fabricated as thin-film elements in order to increase the device impedance. The InSb is norma lly doped n-type to stabilize the electron density and hence the imped ance with respect to temperature changes. This involves tradeoffs, sin ce ionized donors also scatter electrons, reducing their mobility and hence reducing the device sensitivity to a magnetic field. Therefore, optimizing the sensitivity of these devices involves optimizing the do ping of the InSb. This optimization involves three steps. The InSb is undoped for the first 10-20% of the film, forming a buffer from the la ttice-mismatched substrate. The middle, active, layer of the film has a doping gradient. Finally, a thin contact layer is more heavily doped to reduce parasitic contact resistance. (C) 1998 Elsevier Science S.A . All rights reserved.