Study of the Spatial Characteristics of the Breakdown Process in Silicon PN-Junctions
The reduction in the magnitude of resistivity fluctuations in n-type silicon as a result of the neutron transmutation doping process (henceforth the “NTD” process) has had, and will have in the future, significant impact on silicon device technology. Its primary effect should be on high field devices such as high voltage power rectifiers, thyristors, internal gain or “avalanche” photodetectors and nuclear particle detectors. Secondly, minimization of spatial variations in minority carrier lifetime should improve performance of silicon vidicon and image storage devices and, perhaps, improve production yields in the microcircuitry area. Depending upon the degree of enhanced spatial electric field uniformity provided by NTD, such concepts as silicon imaging devices with internal gain may become feasible for the first time. We begin by examining statistically the problem of achieving a high degree of dopant uniformity through NTD. Then, using the tool of a scanned, finely focused, optical beam, we indicate how the spatial area and general characteristics of breakdown can be visualized in silicon PN-junctions fabricated from NTD and other types of silicon. We will present scans of the pre-breakdown and breakdown characteristics of striated, pre-NTD silicon and indicate what we have found to be the physical character of the high voltage breakdown process in that type of silicon.
KeywordsSilicon Crystal Space Charge Region Minority Carrier Lifetime Breakdown Process Internal Gain
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