Gate-Voltage-Induced Switching of the Spin-Relaxation Rate in a Triple-Quantum-Well Structure

Switching of the Dyakonov-Perel spin relaxation owing to the Rashba spin-orbit interaction (SOI) is theoretically studied in a semiconductor heterostructure with three quantum wells. The action of the present spin-relaxation switching is based on the gate-voltage induced electron transfer from the central well with vanishing Rashba SOI to the left or right well with large Rashba SOL The spin-relaxation rate is calculated by extending the Dyakonov-Perel theory of the spin relaxation in a single subband to that in more than one subband in order to take into account the contribution from electrons in excited subbands at higher temperatures. It is shown that the on:off ratio of the spin-relaxation rate at room temperature reaches 10(6) by choosing widths and compositions of well and barrier layers so as to reduce electron population in excited subbands, which gives an undesirable spin relaxation. The present spin-relaxation switching is expected to improve the on:off ratio of the current in the spin-lifetime field effect transistor.