Abstract

Two promising new approaches for designing step recovery diodes (SRDs) for operation at voltages of several hundred volts are considered in this thesis. An entirely new type of step recovery diode is presented, which can operate with reverse voltages of several hundred volts and which exhibits exceptionally long lifetimes of several microseconds. These diodes have been named "wide field step recovery diodes (WFSRDs)". Experimental results for two batches of fabricated devices are presented for 300 V operation into a 50 Ω load. Pulse sharpening operation with rise times as low as 0.9 ns and storage times as large as 9 ns has been observed for fabricated diodes with effective carrier lifetimes of 4500 ns. Pulse sharpening operation has also been observed with rise times as low as 0.6 ns and storage times as large as 30 ns for fabricated diodes with effective carrier lifetimes of 950 ns. These diodes have a diffused p-π-n structure. A comprehensive design theory is developed by considering the nature of the reverse transient in the diode. A method of calculating the breakdown voltage of diffused structures without resorting to simulations is also presented. It is shown that fabrication difficulties will limit the usefulness of the WFSRD to operating voltages below 1 kV.

High-voltage drift step recovery diodes (DSRDs), previously proposed in other work, are also considered. As DSRDs are biased with a pulse, the nature of the forward transient in the diode is considered in detail here. From this, the existing design theory is greatly extended. In particular, the optimum values of the width of the lightly doped layer and the bias current can now be predicted based on the new theory. The maximum storage time consistent with good step recovery action can also now be calculated. These theoretical results are compared to experimental results presented elsewhere, and are in good agreement. It is shown that storage time limitations restrict the use of the DSRD to operating voltages above 1 kV.