Growth and characterization of n-type electron-induced ferromagnetic semiconductor (In,Fe)As

Abstract

We show that by introducing isoelectronic iron (Fe) magnetic impurities and Beryllium (Be) double-donor atoms into InAs, it is possible to grow an n-type ferromagnetic semiconductor (FMS) with the ability to control ferromagnetism by both Fe and independent carrier doping by low-temperature molecular-beam epitaxy. We demonstrate that (In,Fe)As doped with electrons behaves as an n-type electron-induced FMS. This achievement opens the way to realize spin-devices such as spin light-emitting diodes or spin field-effect transistors, as well as helps to understand the mechanism of carrier-mediated ferromagnetism in FMSs.

Electron effective mass in n-type electron-induced ferromagnetic semiconductor (In,Fe)As: Evidence of conduction band transport

“…10 Our (In,Fe)As samples doped with Be behave as an n-type electron-induced FMS, thus solving problem (i). In this letter, we estimate the electron effective mass (m*) and the Fermi level (E F ) of various n-type (In,Fe)As samples by the thermoelectric effect.…”

Interplay between strain, quantum confinement, and ferromagnetism in strained ferromagnetic semiconductor (In,Fe)As thin films

“…7,8 Recently, we have developed an n-type FMS, (In,Fe)As, grown by low-temperature molecular-beam epitaxy (LT-MBE). [9][10][11] Since electron carriers in (In,Fe)As reside in the conduction band of (In,Fe)As with very light effective mass rather than in a hypothetical Fe-related impurity band, (In,Fe)As is a suitable system to test various aspects of carrier-induced ferromagnetism. Indeed, we have demonstrated quantum confinement of electrons in (In,Fe)As quantum wells (QWs) and control of their ferromagnetism by manipulating the wavefunctions of electrons, 12 which have not been realized in Mn-doped FMSs.…”

“…After growing a 100 nm-thick GaAs layer at 550 C, we grew a 500 nm-thick (In 1Ày ,Ga y )As (y ¼ 0.05, 0.1) or (Ga 1Àz ,Al z )Sb (z ¼ 0, 0.5, 1) buffer layers at high temperatures (420 $ 500 C), so that the strain due to the lattice mismatch between the buffer layers and the GaAs substrates was fully relaxed. Then, we grew a 10 nm-thick (In 1Àx ,Fe x )As layer with Be (double donor) 10 doping at 236 C, which is followed by a 5 nm-thick InAs cap layer. The Fe concentration x of the strained (In,Fe)As thin films is fixed at 6%.…”

“…The Be doping concentration n Be in (In,Fe)As is fixed at 4.0 Â 10 19 cm À3 , which gives a positive space charge (ionized donor) density N D of about 1 Â 10 19 cm À3 (Ref. 10). Table I summarizes the structure parameters of our samples.…”

“…The integral is carried out inside the (In,Fe)As layer where the local electron density n is above n th ¼ 6 Â 10 18 cm À3 , which is the threshold for electron-induced ferromagnetism found in our previous study. 10 Note that T 2D C should be a single critical temperature of the whole system, and not the averaged space-dependent Curie temperature. 16 We also include the 2D Stoner enhancement factor A F 2D in the formula of T C…”