Optical Dependence of EDMR in Silicon Devices

Electrically-detected magnetic resonance (EDMR) provides a highly sensitive method for reading out the state of donor spins in silicon. The technique relies on a spin-dependent recombination (SDR) process involving dopant spins that are coupled to interfacial defect spins near the Si/SiO₂ interface. At cryogenic temperatures and low-doping concentrations, optical excitation is used to generate the free carriers. We investigate the wavelength dependence of the EDMR signal in a Si:P device. With near-infrared excitation we find that the EDMR signal primarily arises from donor-defect pairs, while at higher photon energies there are significant additional contributions from defect-defect pairs. At longer wavelengths, the contribution of defect spins adjacent to the buried oxide layer also increased due to the increased penetration depth into the device. Careful tuning of the optical excitation energy allows us to control both the SDR dynamics and to characterize depth-dependent features of the EDMR signal.