Determination of slant angle of p-n interface by multiwavelength near-field photocurrent measurement

Near-field photocurrent measurements with multiwavelength excitation sources are applied to the investigation of a lateral p-n junction grown on patterned GaAs(111)A substrate. In order to probe the internal properties of this device, propagation modes into the sample are utilized retaining high resolution with the contribution of a penetration depth smaller than the aperture diameter. By systematically varying the penetration depth over a wide range up to 900 nm, photocurrent signals due to internal optical response clearly appear. The capability of ''tomographic'' diagnostics is demonstrated and the slant angle of the p-n interface is determined to be 30+/-8 degrees. (C) 1996 American Institute of Physics.