Single‐Crystalline Diluted Magnetic Semiconductor GaN:Mn Nanowires

Abstract

Current information technology relies on two independent processes: charge-based information processing (microprocessors) and spin-based data storage (magnetic hard drives). [1±5] The prospect of simultaneously manipulating both charge and spin in a single semiconductor medium is provided by the exciting area of spintronics. Among many others, diluted magnetic semiconductors (DMSs) represent the most promising candidates for such applications. [1±7] Herein we report on the magneto-and optoelectronic properties of single-crystalline diluted magnetic semiconductor nanowires Ga 1±x Mn x N (x = 0.01±0.09). These nanowires, which have diameters of 10±100 nm and lengths of up to tens of micrometers, exhibit ferromagnetism with Curie temperatures (T C s) above 300 K and magnetoresistances (MRs) up to 250 K. Spin-dependent electron transport from single-nanowire transistors indicates the homogeneous nature of the ferromagnetic nanowires.Gate-dependent conductance and electroluminescence (EL) from nanowire-based light-emitting-diode structures suggest their p-type characteristics, which might support the theory of hole-mediated ferromagnetism. These ferromagnetic GaN:Mn nanowires represent an important class of nanometer-scale building blocks for spintronics.Theoretical studies indicate that transition-metal-doped GaN possesses a ferromagnetic transition temperature higher than room temperature due to hole-mediated ferromagnetism, [8] which would be advantageous for many of the proposed spintronic applications. Many experiments have already been carried out to demonstrate such hypotheses, [9±11] although significant controversy exists over the possibility of magneticimpurity phase separation in many of these thin-film studies. [12±16] Moreover, intrinsic defects in these films originating from the molecular-beam epitaxial growth process may be the Achilles' heel in reaching a fundamental understanding of the ferromagnetism in these materials. On the other hand, the miniaturization of electronic devices represents an ongoing trend for both industrial manufacture and academic research. Among many other possibilities, nanotubes and nanowires are currently being actively explored as possible building blocks for electronic devices with features smaller than 100 nm. [17] The controlled fabrication and fundamental understanding of low-dimensional ferromagnetic semiconductor nanostructures is thus crucial to the development of semiconductorbased spintronic devices and spin-based quantum-computation schemes.Although progress has been made in the understanding of DMS quantum wells and dots, [1±7] studies of quantum wires are still at a nascent stage. Dimensionality and size are known to play a significant role in determining various properties of the systems. [17] In this regard, a one-dimensional (1D) DMS system at the nanometer scale, i.e., a DMS nanowire, is expected to have interesting magnetoelectronic properties and could be a good candidate for realizing spintronic devices for several reasons. First, nanowires themselve...

Ferromagnetism in undoped One-dimensional GaN Nanowires

“…C The discovery of room temperature ferromagnetism (RTFM) 1, 2 in transition metal-doped semiconductors has opened prospects for tailoring the spin and charge phenomena in semiconductor electronics. Since then, there have been continuous reports on RTFM of semiconductors 3 including wurtzite Gallium Nitride (GaN) doped with transition metal ions 4,5 and other non-magnetic impurities. 6 However, the origin of ferromagnetism remains controversial and there are issues such as clustering, segregation, precipitation and formation of secondary phase of the dopants which remain unaddressed.…”

“…1(c)), is ∼0.75 emu/gm which is consistent with the reported values of ∼0.6 emu/gm for Mn-doped GaN nanowires. 4,5 Diamagnetic behavior of 2-μm-thick GaN epitaxial layer grown on Al 2 O 3 (0001) substrate (volume and surface area of GaN epitaxial layer are ∼4 × 10 −5 cm 3 and ∼0.2 cm 2 , respectively) with high temperature AlN buffer by MBE 28 is shown for comparison. The surface area of GaN NWs (∼1.8 cm 2 ) used in VSM studies is very high as compared to the epitaxial layer (0.2 cm 2 ) while the volume of materials employed in both the cases is approximately the same.…”

Magnetic MnxGe1-x Dots for Spintronics Applications

“…The above results are supported by modeling results (Wang and Qian, 2006) although carrier mediated exchange has not yet to be experimentally verified in nanowires. Similarly, high Curie temperatures have been observed in other transition metal doped semiconductor nanostructures such as II-VI (including ZnO (Chang et al, 2003, Cui and Gibson, 2005, Baik and Lee, 2005, ZnS (Brieler et al, 2004, Radovanovic et al, 2005, CdS (Radovanovic et al, 2005)) and III-V (including GaN (Radovanovic et al, 2005, Choi et al, 2005b, GaAs (Jeon et al, 2004)), but only inconclusive reports have been published on the magneto-electric transport in these nanostructures. It could be attributed to the complicated ferromagnetic properties caused by precipitates, second-phase alloys and nanometer-scale clusters.…”

“…Group IV semiconductors are of particular interest to the spintronics technology because of their enhanced spin lifetime and coherent length due to their low spin-orbit coupling and lattice inversion symmetry (Rheem et al, 2007, Choi et al, 2005a. There is also considerable interest for transition metal doped group IV semiconductors (Miyoshi et al, 1999, Park et al, 2002, Tsui et al, 2003, D'Orazio et al, 2004, Li et al, 2005, Demidov et al, 2006, Jamet et al, 2006, Collins et al, 2008, Ogawa et al, 2009, Tsuchida et al, 2009) to the semiconductor industry, owing in part to their excellent compatibility with silicon process technology.…”

Energy production and conversion applications of one-dimensional semiconductor nanostructures

“…Manganese-doped GaN NWs (p-type) grown by a nickel-catalyzed VLS process on n-type SiC substrates demonstrated LED performance [11]. Th ese NWs belong to the special dilute magnetic semiconductor (DMS) class.…”