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Photocurrent-modulated optical nuclear polarization in bulk GaAs
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View: Figures


Image of FIG. 1.
FIG. 1.

Experimental setup (not drawn to scale), placed inside cryostat inserted into a 9.4 T NMR magnet (field parallel to laser beam). The sapphire sample holder was at the tip of a transmission line NMR probe that supplied radio frequency pulses of current through the NMR coil (impedance matching circuit not drawn), which was made of coated copper wire to prevent arcing with the clamps. The dashed lines indicate the circuit built for application of dc voltages across the sample during NMR experiments. The current through the sample was determined by measuring the voltage drop across a resistor in series with the sample.

Image of FIG. 2.
FIG. 2.

Near-band gap photocurrent spectrum for a semi-insulating GaAs sample taken at low voltage. Plotted on the same axes are previously published spectra of optically pumped NMR intensities, measured with no applied electric field (see Ref. 9). The band gap energy is indicated by a vertical dashed line. Error bars are not drawn when smaller than the symbols. The lines are guides to the eyes.

Image of FIG. 3.
FIG. 3.

Top: vs photocurrent for photon energies 1.502 eV (diamonds) and 1.523 eV (triangles, inset). Bottom: vs photocurrent at 1.49 eV for copper contacts (filled squares) and copper plus annealed indium contacts (empty squares). A sample plot of photocurrent as a function of applied electric field (1.49 eV, copper with indium contacts) is shown in the bottom inset. NMR data are scaled relative to the intensity obtained for 1.502 eV photon energy with zero applied voltage, and did not depend on the direction of the applied voltage. Lines are guides for the eyes.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photocurrent-modulated optical nuclear polarization in bulk GaAs