Hybrid ferromagnet-semiconductor gates for nonvolatile memory

A novel magnetoelectronic device for nonvolatile memory applications is presented, and characteristics of a nonvolatile random access memory (NRAM) cell are discussed. In contrast with a magnetoresistive approach, this device uses a single bistable ferromagnetic layer which is electrically isolated from a microstructured semiconducting Hall cross. A micron scale prototype has demonstrated binary output states of 0 and 100 mV (0 and 20 Ω) at room temperature. A submicron cell, with a 0.5 μm by 2.8 μm Permalloy element, has been fabricated and demonstrated excellent properties. Initial sets of prototypes have been fabricated on high mobility III-V semiconductor heterostructures, but the device concept can be used with Si. This novel approach has several advantages. The basic device is a simple bilayer, requiring only two lithographic levels and a single alignment. It is compatible with GaAs or CMOS processing, and device isolation can be readily achieved using Schottky diodes. The simplicity of the device places minimal requirements on fabrication of the ferromagnetic element, and evidence from prototypes suggests high yield. Signal levels are high, and the device shows inverse scalability: smaller devices have improved output characteristics