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

摘要

We explore the bistability effect in a dimensionally scaled semiconductornanostruncture consisting of a diluted magnetic semiconductor quantum dot (QD)and a reservoir of itinerant holes separated by a barrier. The bistabilitystems from the magnetic phase transition in the QD mediated by the changes inthe hole population. Our calculation shows that when properly designed, thethermodynamic equilibrium of the scaled structure can be achieved at twodifferent configurations; i.e., the one with the QD in a ferromagnetic statewith a sufficient number of holes and the other with the depopulated QD in aparamagnetic state. Subsequently, the parameter window suitable for thisbistability formation is discussed along with the the conditions for themaximum robustness/non-volatility. To examine the issue of scaling, anestimation of the bistabiity lifetime is made by considering the thermalfluctuation in the QD hole population via the spontaneous transitions. Anumerical evaluation is carried out for a typical carrier-mediated magneticsemiconductor (e.g., GaMnAs) as well as for a hypothetical case of high Curietemperature for potential room temperature operation.