Pulsed Electrically Detected Magnetic Resonance of 2D Electrons in a Si/SiGe Quantum Well

We have developed a new method of pulsed EDMR (Electrically Detected Magnetic Resonance) and applied it to measure spin relaxation times of 2D electrons in a Si/SiGe quantum well. The method is based on spin-dependent transport in the 2D channel: Conduction electrons scatter off each other, and their scattering cross section depends on the relative orientation of their spins [1]. The initial, thermal polarization of 2D electron spins (at H=350 mT and T=4 K) is altered by applying the resonant 10 GHz microwave pulses. A change in the spin polarization results in a variation of the device conductivity ($\sim $10$^{-4})$, and its recovery back to the thermal equilibrium is measured after the microwave pulse. The recovery time measures the spin relaxation, and we find T$_{1}$ = 1.4 $\mu $s for 2D electrons in a modulation-doped Si quantum well, the same time as we measure with conventional pulsed spin resonance. This new pulsed EDMR method will allow the measurement of T$_{1}$ and T$_{2}$ on small semiconductor structures with sensitivity down to a few spins, possibly a single spin. [1] Ghosh and Silsbee, Phys. Rev. B 42, 12508(1992).