High-Voltage Conductivity-Modulated Silicon Rectifier

Silicon power rectifiers have been made which have reverse breakdown voltages as high as 2,000 volts and forward characteristics comparable to those obtained in much lower voltage devices. It is shown that the magnitude and temperature dependence of the currents can be explained on the basis of space-charge generated current with a trapping level 0.5 eV below the conduction band or above the valence band. The breakdown voltage of a P + IN + diode is computed from avalanche multiplication theory and is shown to be a function of the width of the nearly intrinsic region. A simple diffusion process is evaluated and shown to be adequate for diode fabrication. The characteristics of devices fabricated from high-resistivity compensated, floating-zone refined, and gold-doped silicon are presented. The surface limitation to high inverse voltage rectifiers is discussed.