Report on the Work on Discrete Devices: High Voltage Transistors and Varactor Diodes

Abstract

The important electrical parameters (such as breakdown voltage, current gain and rating, power dissipation, switching times, saturation voltage etc.) of the high-voltage power transistor are achieved by controlling the physical parameters of the device such as base and collector resistivities, widths and emitter geometry. There are several tradeoffs necessary, such as between high voltage rating and current gain or saturation voltage.Triple-diffusion technology has been chosen for the voltage ratings above 1000 V in comparison with other technologies. Methods of passivation such as surface contouring, surface coatings are chosen from considerations of ease of operation, yield and cost considerations so as to give low leakage with the high voltage requirement. For attaining the current rating, the choice of metallization is important. Some of the results obtained are: BVCEO(1A)=1000 V, BVCBO= 1500 V, hFE=2 to 5.The electrical parameters of tuning varactor (for the VHF and UHF bands) are the capacitance ratio at the working voltage range, the quality factor at the frequencies of operation and variation of tuning with voltage.The retrograde impurity profile is achieved by precise control of diffusion of impurities; C(3)/C(25) of 4 to 6 has been achieved. High Q is achieved by low series resistance and low leakage current.