Monte Carlo investigation of electron spin relaxation in GaAs crystals during low-field transport

Abstract

A great emerging interest within the condensed matter physics is the use of electron spin in semiconductor-based spintronic devices to perform both logic operations, communication and storage. In order to make spintronics a feasible technology, sufficiently long spin lifetimes and the possibility to manipulate, control and detect the spin polarization are required. The loss of spin polarization before, during and after the necessary operations is a crucial problem into spin device design; thus, a full understanding of the role played by the lattice temperature, the doping density and the amplitude of the applied electric field on the electron spin dynamics in semiconductors is essential for the design and fabrication of spintronic devices. In recent years many experiments have been carried out with the aim of study the influence of transport conditions on relaxation of electron spins in semiconductors, but they are mainly focused on the analysis of spin lifetimes at very low temperatures (T<10 K). Despite a lot of theoretical or simulative works have been devoted to the investigations of non-equilibrium spin relaxation, till today, to the best of our knowledge, an investigation of influence of lattice temperature on the spin depolarization time up to room temperature in the presence of driving electric fields in semiconductor bulk structures, for different values of the doping density, is still missing. Aim of this work is to analyze the influence of the lattice temperature on electron spin lifetimes in n-type GaAs crystals driven by low-amplitude electric fields. The transport of electrons is simulated by using a semiclassical Monte Carlo approach [1], which takes into account the intravalley scattering mechanisms of warm electrons in the semiconductor material and includes the spin polarization vector [2-3]. Spin relaxation is considered through the D'yakonov-Perel mechanism [4], which is dominant in the investigated range of temperature (40 < T < 300 K) [5]. The evolution of spin polarization is studied by analyzing the computed lifetimes as a function of the doping density in the range 10^{13}- 10^{16} cm^{-3} (non-degenerate regime), in the presence of a static electric field with amplitudes in the range 0.05-0.5 kV/cm. Our findings show that the electron spin lifetime is not marginally influenced by the intensity of the driving electric field, the lattice temperature and the impurity density, which hence represent key parameters into the depolarization process.