Studies on the growth and characterization of rare-earth Gd-Doped InGan/Gan magnetic semiconductor heterostructures
Spintronics is an emerging field in which the spin of carriers in addition to the charge of carriers can be used to achieve new functionalities in electronic devices. The availability of materials exhibiting ferromagnetism above room temperature is prerequisite for realizing such devices. Materia...
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| Format: | Thesis |
| Language: | English |
| Published: |
2011
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/3087/1/24p%20SITI%20NOORAYA%20MOHD%20TAWIL.pdf |
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| Summary: | Spintronics is an emerging field in which the spin of carriers in addition to the
charge of carriers can be used to achieve new functionalities in electronic devices. The
availability of materials exhibiting ferromagnetism above room temperature is
prerequisite for realizing such devices. Materials suitable for spintronic applications are
desired to be compatible with conventional growth and fabrication techniques in
addition to exhibiting above room temperature ferromagnetic properties.
In this research, the growth of InGaGdN epilayers have been achieved on (0001)
sapphire substrates or metalorganic vapor phase epitaxy (M0VPE)-grown GaNIsapphire
templates by plasma-assisted molecular beam epitaxy (MBE) using elemental Ga, In, Gd
and Si (co-doping) and gaseous N 22 as sources. Magnetic characterization of the grown
epilayers was performed by a superconducting quantum interference device (SQUID)
magnetometer. Ferromagnetic properties were observed at room temperature for this
new type of quaternary alloy material. Co-doping of InGaGdN with Si was performed
and increase in shallow donor density as well as enhancement in ferromagnetic
properties were achieved. Luminescence properties of InGaGdN were also observed at
room temperature with the emission peak energy red-shifts corresponding to the InN
molar fraction. Gd incorporation into InGaN epilayers were confirmed by X-ray
absorption fine structure (XAFS) analysis revealing that ~ dd??'' ions substitutionally
occupy the cation sites of Ga of host material.
MBE growth of multi-layer structures i.e. InGaGdNIGaN multiple-quantum well
(MQW) was also carried out and its characteristic were investigated. The InGaGdNIGaN
MQW samples showed clear hysteresis and clear saturation in the magnetization versus
magnetic field curve with larger magnetization per unit volume than the InGaNIGaGdN
MQW samples implying that carrier (electron) induced ferromagnetism occurs in such
heterostructures. Better structural qualities have been achieved for the Si-doped barrier
layers of InGaGdNIGaN samples in which more pronounced satellite peaks can be
observed from the X-ray diffraction curves compared to the undoped barrier sample Adding Si in the barrier layers has further enhanced the ferromagnetic properties as well
as electrical properties of the MQW structure samples.
This work has provided useful experimentally based insights into GaN-based
diluted magnetic semiconductors (DMSs), resulting in the development of
semiconducting materials that show room temperature ferromagnetism. These materials
could pave the way for development of multifunctional microelectronic devices that
integrate electrical, optical, and magnetic properties particularly for the development of
spin-based-electronic devices |
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