Zero field EDMR
Although semiconductor devices are ubiquitous in today's economy, many of the most exciting recent demonstrations of spin-dependent effects have taken place in minority states within these materials. Such minority states can be, for example, charges localized to particular defects, dopants, or even other charges. Once trapped in this way, these charges can be utilized as sensitive probes of their local environments. By using electrically detected magnetic resonance (EDMR) as a means of manipulating and observing the spin state of such charges, much information can be gained about the nature of these defects, dopants, and excitations, as well as their microscopic environment.
One rather unique method of EDMR is the detection of a spin resonance condition existing at exceedingly small magnetic fields, on the order of Earth's own field (~0.5 Gauss). This manifests as a change in material resistivity, of a few thousand percent in some cases, while sweeping magnetic field through the zero condition. Depending on the community, these observations are called zero-field spin-dependent recombination or simply an ultra-small-magnetic-field effect. Regardless of label, the microscopic mechanisms thought responsible for this zero-field signal vary amongst the materials which display this effect and great ambiguity currently exists even for single material types, especially where there seem to be competing mechanisms of a similar order.
Given that such nearly-negligible interaction energies at small fields can give rise to electronic changes at energy scales over a million times larger is striking. Yet, in order to engineer these effects for device applications, an understanding of the microscopic mechanisms responsible must be made. To that end, our reseach group is conducting EDMR experiments at, and around, zero field for a variety of semiconductor materials.