Operational Calculation of Puncture Voltage of Drift n-p-n Transistors in Inverse Mode

Abstract

The article deals with the issues of the operational calculation of the breakdown voltages of drift n-p-n transistors in the inverse operating mode when calculating the parameters of their structure according to the given electrical parameters and characteristics. When calculating the parameters of the structure of a bipolar drift transistor, the concentrations at the collector-base (NCB) and emitter-base (NEB) p-n junctions are determined for a given avalanche breakdown voltage. The limitation of the minimum base thickness (WB.min) is determined by the given value of the voltage of the transistor base puncture and by a certain calculated impurity concentration between the concentrations of NCB and NEB. The calculated impurity concentrations in the base of the drift transistor in the forward and inverse modes of operation differ significantly. The technological experiment was carried out on silicon wafers with two different impurity concentrations in epitaxial structures and with different base thicknesses, as indicated by different values of the current amplification factors both in the direct and inverse connections. The concentration values were determined by calculating NCB and NEB according to the known boron diffusion mode to form the transistor base regions. The depths of p-n junctions were determined by the ball-thin section method. The electrical parameters of the transistors in direct and inverse connections were measured on an Л2-56 semiconductor device meter. Based on experimental data, the calculated impurity concentration in the base of the drift transistor is determined from the values of NCB and NEB. The resulting calculation expression can also be used to calculate the base voltage of drift n-p-n transistors in the inverse operating mode, the base voltage of switching transistors in I 2 L elements, as well as to calculate the area of the reverse gradient of ultra-sharp varicaps.