Non-volatile bistability effect based on electrically controlled phase transition in scaled magnetic semiconductor nanostructures

TL;DR

This paper investigates electrically controlled magnetic phase transition-induced bistability in scaled magnetic semiconductor nanostructures, highlighting potential for non-volatile memory applications and analyzing stability at different scales.

Contribution

It introduces a design for bistability in magnetic semiconductor quantum dots mediated by hole population changes, including scaling effects and stability analysis.

Findings

Bistability can be achieved at two distinct magnetic states in scaled structures.

Parameter windows for bistability depend on design and material properties.

Estimated bistability lifetime indicates potential for non-volatile operation.

Abstract

We explore the bistability effect in a dimensionally scaled semiconductor nanostruncture consisting of a diluted magnetic semiconductor quantum dot (QD) and a reservoir of itinerant holes separated by a barrier. The bistability stems from the magnetic phase transition in the QD mediated by the changes in the hole population. Our calculation shows that when properly designed, the thermodynamic equilibrium of the scaled structure can be achieved at two different configurations; i.e., the one with the QD in a ferromagnetic state with a sufficient number of holes and the other with the depopulated QD in a paramagnetic state. Subsequently, the parameter window suitable for this bistability formation is discussed along with the the conditions for the maximum robustness/non-volatility. To examine the issue of scaling, an estimation of the bistabiity lifetime is made by considering the thermal fluctuation in the QD hole population via the spontaneous transitions. A numerical evaluation is carried out for a typical carrier-mediated magnetic semiconductor (e.g., GaMnAs) as well as for a hypothetical case of high Curie temperature for potential room temperature operation.