We have studied the current-induced displacement of a domain wall (DW) in the permalloy (Py) layer of a Co/Cu/Py spin valve structure at zero and very small applied field. The displacement is in opposite direction for opposite dc currents, and the current density required to move DW is only of the order of 10 6 A/cm 2 . For H = 3 Oe, a back and forth DW motion between two stable positions is observed. We also discuss the effect of an applied field on the DW motion.

A near-infrared (NIR) enhanced silicon single-photon avalanche diode (SPAD) fabricated in a customized 0.13 µm CMOS technology is presented. The SPAD has a depleted absorption volume of approximately 15 µm × 15 µm × 18 µm. Electrons generated in the absorption region are efficiently transported by drift to a central active avalanche region with a diameter of 2 µm. At the operating voltage, the active region contains a spherically uniform field peak, enabling the multiplication of electrons originating from all corners of the device. The advantages of the SPAD architecture include high NIR photon detection efficiency (PDE), drift-based transport, low afterpulsing, and compatibility with an integrated CMOS readout. A front-side illuminated device is fabricated and characterized. The SPAD has a PDE of 13% at wavelength 905 nm, an afterpulsing probability < 0.1% for a dead time of 13 ns, and a median dark count rate (DCR) of 840 Hz at room temperature. The device shows promising performance for time-of-flight applications that benefit from uniform NIR-sensitive SPAD arrays.

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