title: Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR.
abstract: The nanoscale distributions of electron density and electric fields in GaAs semiconductor devices are displayed with NMR experiments. The spectra are sensitive to the changes to the nuclear-spin Hamiltonian that are induced by perturbations delivered in synchrony with a line-narrowing pulse sequence. This POWER (perturbations observed with enhanced resolution) method enhanced resolution up to 10(3)-fold, revealing the distribution of perturbations over nuclear sites. Combining this method with optical NMR, we imaged quantum-confined electron density in an individual AlGaAs/GaAs heterojunction via hyperfine shifts. Fits to the coherent evolution and relaxation of nuclei within a hydrogenic state established one-to-one correspondence of radial position to frequency. Further experiments displayed the distribution of photo-induced electric field within the same states via a quadrupolar Stark effect. These unprecedented high-resolution distributions discriminate between competing models for the luminescence and support an excitonic state, perturbed by the interface, as the dominant source of the magnetically modulated luminescence.
authors.affiliation: A. A. Noyes Laboratory of Chemical Physics, M/S 127-72, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Kempf
authors.forename: Michael A
authors.initials: MA
authors.lastname: Miller
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Weitekamp
mesh_terms: D004583:Electrons; D049449:Luminescence; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics; D011789:Quantum Theory