Coexistence of ferromagnetism and quantum Hall effect in Mn modulation-doped two-dimensional hole systems

Abstract

Modulation doping using Mn as an acceptor has been applied to the molecular beam epitaxial grown compressively strained InAs channels. Strain engineering has been accomplished by the growth of a graded, fully relaxed InxAl1-xAs buffer layer on GaAs(0 0 1) substrates in which the In content x was increased from 0% to 75%. Transmission electron microscopical investigation of the heterostructures reveals the high quality of the heterostructures grown on top of the metamorphic buffer layer. Significant segregation and diffusion of the Mn doping profile is confirmed by secondary ion mass spectroscopical analysis. Both normal as well as inverted doped quantum well structures show pronounced Shubnikov-de Haas oscillations and quantum Hall effect plateaus. However, for the inverted heterostructures where a significant Mn concentration within the InAs channel can be detected, a strong resistance maximum at B=0 T accompanied by a hysteretic behaviour and reproducible resistance jumps indicative of ferromagnetic ordering is observed.