Enhancement of Curie temperature in Ga(1-x)Mn(x)As/Ga(1-y)Al(y)As ferromagnetic heterostructures by Be modulation doping

TL;DR

Modulation doping with Be in Ga(1-x)Mn(x)As/Ga(1-y)Al(y)As heterostructures significantly increases the Curie temperature, with the effect depending on the doping sequence, aligning with theoretical predictions of carrier-mediated ferromagnetism.

Contribution

This study demonstrates that Be modulation doping can enhance the Curie temperature in GaMnAs heterostructures, revealing the importance of doping sequence and Fermi energy during growth.

Findings

Curie temperature increases from 70 K to over 100 K with Be doping.

The increase occurs only when Be is doped after magnetic layer deposition.

Results align with multi-band mean field theory simulations.

Abstract

The effect of modulation doping by Be on the ferromagnetic properties of Ga(1-x)Mn(x)As is investigated in Ga(1-x)Mn(x)As/Ga(1-y)Al(y)As heterojunctions and quantum wells. Introducing Be acceptors into the Ga(1-y)Al(y)As barriers leads to an increase of the Curie temperature T_C of Ga(1-x)Mn(x)As, from 70 K in undoped structures to over 100 K with the modulation doping. This increase is qualitatively consistent with a multi-band mean field theory simulation of carrier-mediated ferromagnetism. An important feature is that the increase of T_C occurs only in those structures where the modulation doping is introduced after the deposition of the magnetic layer, but not when the Be-doped layer is grown first. This behavior is expected from the strong sensitivity of Mn interstitial formation to the value of the Fermi energy during growth.