Magnetoelectronics in semiconductor devices

This work is a theoretical study of a particular concept of field effect tr ansistor, the spin-FET. This structure consists of a high electron mobility transistor (HEMT) where usual highly doped source and drain regions are re placed by ferromagnetic contacts. The source contact acts as a spin polariz er for the electrons injected in the conduction channel of the HEMT and the drain contact as a spin detector for electrons reaching the end of the cha nnel. So, the drain current depends on the comparison of the spin orientati on of electrons reaching this contact with the magnetic moment orientation of the drain. Furthermore, the control of the electron spin orientation by the gate voltage is possible in the channel of a HEMT. The spin-FET is ther efore a device in which the current is controlled magnetically by the gate voltage, in addition to the classical field effect control which consists i nto the modulation of the electron density in the channel. After reviewing the spin dephasing effects appearing ill such structures and comparing thei r respective influences, we describe the model that we develop to study spi n-polarized transport in the channel of a HEMT. Then, we study the spin-FET , as a structure for the investigation of the physics of spin, polarized tr ansport in ferromagnet/semiconductor structures and as a device for fast el ectronics. These results point out the importance of the properties of ferr omagnet/semiconductor contacts for spin-FET performances. We close this stu dy with some considerations about these contacts and describe the approach that we develop now to model them.