High-voltage planar junctions investigated by the OBIC method

The optical-beam-induced currents (OBIC) method and its application to high-voltage planar junctions will be introduced. Measurements are performed on a p⁺-n diode with a cylindrical junction edge. These measurements illustrate the response of the OBIC signal when negative or positive surface charges are present. It will be shown that multiple field ring structures, which are difficult to optimize, can be improved by combining OBIC measurements with Brieger´s model. A fieldring structure with four rings is optimized to block 1550 V on a 9 × 10¹³n-substrate. In a reverse-biased planar junction the point of maximum carrier multiplication is found to be some micrometers below the surface (depending on the junction depth). We used the wavelength dependence of the OBIC signal to show that a variation of lateral doping (VLD) structure with 20-µm junction depth breaks down between 5 and 10 µm below the surface.