Effects of multi-subband occupation and electric field in ferromagnetic semiconductor quantum wells

Ferromagnetism in III–V diluted magnetic semiconductor (DMS) quantum wells is studied theoretically paying special attention to the occupation of multiple subbands by holes and the effect of static electric field perpendicular to the well plane. Our calculations show that the ferromagnetic transition temperature Tc of DMS quantum-well exhibits step-function-like dependence on the carrier concentration, reflecting the quasi-two-dimensional nature of systems. The Tc can be sensitively controlled by the application of electric field when the hole density is small so as to occupy only a few subbands.