Hybrid ferromagnet–semiconductor devices

Abstract

Novel magnetoelectronic devices for application as nonvolatile memory cells, logic gates, or magnetic field sensors are based on a bilayer structure comprised of a high mobility semiconducting Hall cross and a single, electrically isolated, microstructured ferromagnetic film. Prototypes have been fabricated at the micron and sub-micron size scale. The device state is determined by the bistable magnetic state of the ferromagnetic element, and the two corresponding output states can be symmetrically bipolar or HIGH (order of tens of ohms) and LOW (approximately zero). Fabrication involves two lithographic steps, a mesa etch of the semiconductor and a patterning of the ferromagnetic film. Atomic force microscope and magnetic force microscope images are used to correlate the effects of processing on the micromagnetism of the ferromagnetic component and the device output characteristics. Early prototype device sets have been fabricated using high mobility indium arsenide layers for the Hall element, but the concept is compatible with silicon technology. The device demonstrates inverse scalability: output levels increase as the device dimensions decrease.