High- Voltage Conductivity-Modulated 

 Silicon Rectifier 



By H. S. VELORIC and M. B. PRINCE 



(Manuscript received May 1, 1957) 



Silicon power rectifiers have been made which have reverse breakdown volt- 

 ages 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 con- 

 duction 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 shoivn 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 limi- 

 tation to high inverse voltage rectifiers is discussed. 



I IXTKODL'CTION 



The desire for high voltage rectifiers in the electronic industry has 

 pushed the peak inverse voltage of solid state rectifiers to higher and 

 higher values. The purpose of this paper is to present some of the con- 

 siderations necessary in designing a device with a high iuA^erse voltage 

 and an excellent forward characteristic. In many cases the device charac- 

 teristics are predictable. Conversely, high Noltage diodes are excellent 

 tools for studying many solid state phenomena. 



It has been shown^ that it is possible by the use of the conductivity 

 modulation principle to separate the design of the forward current-volt- 

 age characteristic from the reverse current- voltage characteristic of a 

 silicon p-n junction rectifier. Units have been fabricated by the difTusion 

 of boron and phosphorus into high resisti\'ity material, that have reverse 

 breakdown voltages in the range of 1,000 to 2,000 volts. 



The reverse currents are of the order of a microampere per scjuare cen- 

 timeter at room temperature and increase approximately as the square 



975 



