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Print Submitted on July 02, 08:30 PM for mmm2010 Proof CONTROL ID: 923311 TITLE: Geometric enhancement of electrical spin injection and detection in semiconductors for high temperature operation AUTHORS (LAST NAME, FIRST NAME): Adari, R.1; Murthy, M.1; Patil, T.1; Maheshwari, R.1; Vaidya, G.1; Ganguly, Swaroop1; Saha, Dipankar 1 INSTITUTIONS (ALL): 1. Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India. ABSTRACT BODY: The effects of feature sizes on the characteristics of lateral semiconductor spintronic devices have been investigated experimentally and theoretically. It is demonstrated that confining spin-transport in the active region of a device enhances magnitude of the spin-dependent response substantially. Numerical simulation of spin-transport corroborates the experimental observations. We have fabricated and measured magnetoresistance in local and non-local epitaxially grown MnAs/GaAs lateral spin-valves for ferromagnetic source and drain contact widths varying from 1 µm to 10 µm. We have also fabricated devices with various mesa sizes to study the effect of confinement on spin transport [1,2]. We have observed that the magnetoresistance reaches peak for an optimum contact width of ~0.35xLn, where Ln is the spin-diffusion length in semiconductor. The magnetoresistance is negligible for very large and very small contact widths. We have measured a peak magnetoresistance of ~0.2% at 250 K. We also demonstrate theoretically and experimentally that ferromagnetic contact length, width and channel length dimensions are key to the high temperature spin injection and detection in semiconductors. The non-monotonic dependence of spin-dependent response on device geometry is explained in the two-dimensional spin-diffusion framework. It is concluded that smaller contact pads compare to the spin-diffusion length act very poorly as spin injector and detector as the advantage of long spin-coherence length in semiconductors is under-utilized in this case. Spin relaxation under the contact region dominates for very large contacts, which reduces spin injection and detection efficiency. These two competing effects give rise to optimum dimensions where the effect is maximum. The experimental observations can be extended to any lateral spintronic device including spin lasers, spin-transistors, and spin-modulators. References: [1] Saha et. al., Appl. Phys. Lett. 92, 022507 (2008). [2] Dery et. al., Phys. Rev. B 73, 041306 (2006). KEYWORDS: spin-injection, spin-detection, spin-valve, spintronic. (No Image Selected)
Abstract Details PRESENTATION TYPE: Oral CATEGORY: III. Spintronics SUB-CATEGORY: H. Spin Injection (Semiconductors) Visa Information: Yes Visa Application: No Previous Presentation: No Sector: i. academia
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