No abstract

Time-resolved Faraday rotation is used to measure electron spin coherence in n-type GaN epilayers. Despite densities of charged threading dislocations of ϳ5ϫ10 8 cm Ϫ2 , this coherence yields spin lifetimes of ϳ20 ns at Tϭ5 K, and persists to room temperature. Spin dephasing is investigated in the vicinity of the metal-insulator transition. The dependence on both magnetic field and temperature is found to be qualitatively similar to previous studies in n-type GaAs, suggesting a common origin for spin relaxation in these systems.

We investigate spin-polarized inter-band tunneling through measurement of a (Ga,Mn)As based Zener tunnel diode. By placing the diode under reverse bias, electron spin polarization is transferred from the valence band of p-type (Ga,Mn)As to the conduction band of an adjacent n-GaAs layer. The resulting current is monitored by injection into a quantum well light emitting diode whose electroluminescence polarization is found to track the magnetization of the (Ga,Mn)As layer as a function of both temperature and magnetic field.

A fourteen-fold anisotropy in the spin transport efficiency parallel and perpendicular to the charge transport is observed in a vertically-biased (Ga,Mn)As-based spin-polarized light emitting diode. The spin polarization is determined by measuring the polarization of electroluminescence from an (In,Ga)As quantum well placed a distance d (20-420 nm) below the p-type ferromagnetic (Ga,Mn)As contact. In addition, a monotonic increase (from 0.5 to 7%) in the polarization is measured as d decreases for collection parallel to the growth direction, while the in-plane polariza tion from the perpendicular direction (~0.5%) remains unchanged.