Magnetic detection of photogenerated currents in semiconductor wafers using superconducting quantum interference devices

A completely noninvasive method is presented for the investigation of semic onductor wafers with high spatial resolution utilizing a superconducting qu antum interference device (SQUID) magnetometer system. The method is based on the detection of the magnetic field caused by photocurrents generated in the semiconductor sample using a sensitive SQUID magnetometer. The photocu rrents arise when laser light with a photon energy exceeding the band gap o f the semiconductor is focused onto the sample surface in a region of a dop ing gradient. The spatial resolution of this detection method is mainly det ermined by the size of the excitation focus of about 20 mm. We report on me asurements of silicon wafers with small growth-related doping fluctuations. (C) 1999 American Institute of Physics. [S0003-6951(99)01819-7].