Modulating room temperature spin injection into GaN towards the high-efficiency spin-light emitting diodes

Abstract

Spin injection performance in GaN film was systematically investigated through the three-terminal Hanle spin precession measurements with the comparison of varied tunnel barrier thickness, spin injector materials, and channel widths. Spin relaxation time and diffusion length were optimized to 37.3 ps and 139.0 nm at room temperature, respectively. With the optimal spin injector, a 12% spin polarization was obtained in a four-terminal non-local spin valve device. By applying the optimized spin injector structure to the spin-light emitting diodes, room temperature circular polarization ratios of 6.2% and 9.2% for Co and Fe spin polarizers were respectively achieved at surface-emission.

High-Efficient Spin Injection in GaN at Room Temperature Through A Van der Waals Tunnelling Barrier

“…By employing the above parameters (a effective cross-sectional area of 1.2 × 10 –12 m 2 , a resistivity of 0.11 Ω·m for ~ 10 18 cm −3 n-GaN measured through the four-probe method), the spin polarization is estimated to be about 9.0% and 14.5% for the two devices, respectively. To our knowledge, the spin polarization value with bilayer h-BN is higher than any previous report for the spin injection in GaN [ 5 , 11 – 13 ]. There are two possible reasons for the better performance of bilayer h-BN.…”

“…2 b, c, the three-terminal device with Fe (Co) ferromagnetic electrode produces a 65 (52) μV spin accumulation signal. The calculated spin relaxation time and spin diffusion length are 42 (46) ps and 165 (173) nm, respectively, which are significantly increased than the cases of using the Al 2 O 3 tunnelling layer [ 5 , 6 ]. This is due to the smooth two-dimensional nature of the h-BN film and the sharp van der Waals interface for the Fe (Co)/h-BN/GaN trilayer.…”

“…Semiconductor spintronic devices, which combine electrical charge and spin as information carriers [1], bring new prospects for developing next-generation integrated circuits [2]. III-nitride semiconductors such as GaN, which are widely used in high-performance electronic and optoelectronic devices [3][4][5][6], are also promising candidates for energy-efficient spintronic applications. Electrical spin injection is a common route towards functionalized semiconductors spintronic devices [1].…”

“…To eliminate the conductivity mismatch between ferromagnetic metals (FM) and semiconductors [7,8] and achieve high-efficient spin injection and transport, an extremely thin dielectric layer should be inserted as a tunnelling layer at the metal-semiconductor interface [9]. The conventional tunnelling layers used in spintronic devices are oxides, such as Al 2 O 3 [5,6,10] and MgO [11][12][13], which can improve the tunnelling spin polarization by regulating the height of the tunnelling barriers [14][15][16]. However, achievement of high spin selectivity is still faced with difficulties including pinholes caused by nonuniform thickness of oxides [17,18], and spin scattering induced by lattice mismatch [12].…”

Half‐Metallic Heusler Alloy/GaN Heterostructure for Semiconductor Spintronics Devices

“…[11] Because of the intrinsically weak spin-orbit coupling in GaN, [12][13][14] the possibility of semiconductor spintronic devices such as a spin LED [15][16][17] and spin field-effect transistor [18,19] has also emerged in the field of GaN systems. Thus far, it has been demonstrated, even at room temperature, electrical spin injection into GaN in LED structures [20][21][22][23] and three-or four-terminal lateral device structures. [23][24][25][26][27][28][29] However, almost all of the previous related studies have used an insulating tunnel barrier such as MgO and AlN for electrical spin injection into GaN to solve the spin resistance mismatch problem, [30][31][32] resulting in high-resistance contacts with a resistance-area product (RA) higher than several MΩμm 2 .…”