09:15 〜 09:30
▲ [20a-D104-2] Epitaxial growth and magnetic properties of Fe delta-doped InAs thin films
キーワード：ferromagnetic semiconductor, delta-doping
Among various ferromagnetic semiconductors (FMSs), (In,Fe)As, the first n-type electron-induced III-V FMS [1,2], is particularly promising. Using low-temperature molecular beam epitaxy (LT-MBE), Fe atoms are doped and randomly distributed in the host InAs crystal structure [1]. Various novel features such as large s-d exchange interaction energy [2,3], and a large spontaneous spin splitting [4] were observed in the conduction band of (In,Fe)As thin films. However, TC of these (In1-x,Fex)As thin films are still much lower than room temperature (~50 K), which is partly because of their low Fe concentrations x (x = 6 - 8%). To increase x is, however, challenging because of the low solubility of Fe in III-V semiconductors.
Here we study the growth and magnetic properties of InAs thin films, in which Fe atoms are delta-doped with a thickness of one monolayer (ML), thus realizing very high local density of Fe. The samples under study were grown by MBE on InAs (001) or semi-insulating GaAs (001) substrates. The Fe delta-doping MLs and their upper layers were grown at a low growth temperature of 236℃. Scanning transmission electron microscopy (scanning TEM) images of a Fe-As ML (the nominal x in this ML is 100%) grown between InAs layers show only zinc-blende structure of the host InAs. Along the z direction, the Fe atom distribution, obtained by energy dispersive X-ray spectroscopy (EDX), is found to obey the normal distribution with a standard deviation σ = 0.45 nm or 1.5 InAs ML (the spatial resolution of the EDX measurement is 3 - 4 InAs ML). These data indicate that the Fe delta-doped InAs thin films were successfully grown. Next, we grew samples with a 12 nm-thick InAs layer on a AlSb buffer layer/GaAs (001) substrates. Inside this 12 nm-thick InAs layer, Fe-As MLs (totally N layers, N = 1,3,5,7) were grown with a regular interval of InAs t MLs. All samples exhibit intrinsic ferromagnetism, with the TC value increases rapidly with decreasing t, reaching 80 K for N = 7. Furthermore, in these samples, the magnetic moment per Fe atom at saturated magnetization is estimated to be 5 μB, which is the ideal value of the Fe3+ ions. These results indicate that Fe delta-doping is a promising approach to optimize the magnetic properties of (In,Fe)As for device applications.
References [1] P. N. Hai, et al., APL 101, 182403 (2012). [2] P. N. Hai, et al., APL 101, 252410 (2012). [3] L. D. Anh, et al., APL 104, 042404 (2014). [4] L. D. Anh et al., Nature Comm. 7, 13810 (2016).
Here we study the growth and magnetic properties of InAs thin films, in which Fe atoms are delta-doped with a thickness of one monolayer (ML), thus realizing very high local density of Fe. The samples under study were grown by MBE on InAs (001) or semi-insulating GaAs (001) substrates. The Fe delta-doping MLs and their upper layers were grown at a low growth temperature of 236℃. Scanning transmission electron microscopy (scanning TEM) images of a Fe-As ML (the nominal x in this ML is 100%) grown between InAs layers show only zinc-blende structure of the host InAs. Along the z direction, the Fe atom distribution, obtained by energy dispersive X-ray spectroscopy (EDX), is found to obey the normal distribution with a standard deviation σ = 0.45 nm or 1.5 InAs ML (the spatial resolution of the EDX measurement is 3 - 4 InAs ML). These data indicate that the Fe delta-doped InAs thin films were successfully grown. Next, we grew samples with a 12 nm-thick InAs layer on a AlSb buffer layer/GaAs (001) substrates. Inside this 12 nm-thick InAs layer, Fe-As MLs (totally N layers, N = 1,3,5,7) were grown with a regular interval of InAs t MLs. All samples exhibit intrinsic ferromagnetism, with the TC value increases rapidly with decreasing t, reaching 80 K for N = 7. Furthermore, in these samples, the magnetic moment per Fe atom at saturated magnetization is estimated to be 5 μB, which is the ideal value of the Fe3+ ions. These results indicate that Fe delta-doping is a promising approach to optimize the magnetic properties of (In,Fe)As for device applications.
References [1] P. N. Hai, et al., APL 101, 182403 (2012). [2] P. N. Hai, et al., APL 101, 252410 (2012). [3] L. D. Anh, et al., APL 104, 042404 (2014). [4] L. D. Anh et al., Nature Comm. 7, 13810 (2016).