The Use of Quantum Point Contacts for Spintronics Applications

Abstract

A field effect transistor based on spin rather than charge (a SpinFET, Spin Field Effect Transistor) was first proposed by Datta and Das in 1990 [1]. Since then, many approaches have been pursued to achieve spin injection, detection and manipulation in semiconductors either by incorporating ferromagnetic materials into device architectures or by using external magnetic fields [2,3]. However, both these approaches add significant design complexity because the magneto-resistance and the stray magnetic fields of the ferromagnetic contacts influence device performance and hamper use in integrated circuits. In addition, the conductivity mismatch between the ferromagnetic contacts and semiconducting channel limits the efficiency of spin injection, and this is detrimental to the ON/OFF current ratio [4]. In fact, the full potential of spin-based devices can only be realized if injection, manipulation, and detection of the electron spin can be performed by purely electrical means [5]. Several attempts towards this goal have been reported over the last ten years using devices such as quantum point contacts (QPCs) and quantum dots. In this talk we will review some the most recent work in these areas using QPCs with top and in-plane side gates [6,7]. These new developments could lead to the realization of an all-electric Datta-Das SpinFET which could be used in the design of all-electric spin-based sensors, spin filters and interferometers, with potential for multilevel logic circuits and data storage applications. They could also be used as building blocks in architectures for future quantum information and quantum computing applications. However, the large scale integration of the all-electric SpinFET will require an assessment of their reliability, and recent conductance measurements on large arrays of nominally identical QPCs show that this task still remains a formidable technological challenge [8-10]. References [1] Datta S. and Das B., Appl. Phys. Lett. 56, 665 (1990). [2] Zutic I., Fabian J., and Sarma S.D., Rev. Mod. Phys. 76, 323 (2004). [3] Bandyopadhyay S. and Cahay M., Introduction to Spintronics, CRC Press (Boca Raton, FL), (2008). [4] Schmidt G. et al., Phys. Rev. B 62, R4790 (2000). [5] Awaschalom D