No abstract

The fast current interruption property of DriftStep Recovery Diodes (DSRDs) is utilized in high voltage fast switches. Previously, using a physical device simulator, we have conducted a theoretical investigation of this mechanism in a p + πn + structure and evaluated the expected dependence of device performances on its structure and driving conditions. In this letter, we experimentally validate these findings by presenting consistency between the theoretical results, and the actual measured results. Diode structures with a uniform doping profile and abrupt junction were fabricated using thick layer epitaxy technology, which allows for improved control over the doping profile, compared to the traditional method of deep aluminum diffusion. The switching characteristics of the diodes were measured using a specially designed circuit. An outstanding switching time of 0.3 ns at 230 V per DSRD die was demonstrated by driving the diode with a reverse current density exceeding 1250 A/cm 2 . We conclude that a semi-empirical design of the diode and its driving conditions can be substituted by accurate modeling using the device simulator. By combining the physical understanding gained with accurate modeling capabilities and epitaxial growth technology, novel diode design and improved switching performance may be achieved.Index Terms-High voltage, fast switching, sub-nanosecond, drift step recovery diode, thick layer Epitaxy, opening switch.

A silicon-avalanche shaper/sharpener is a fast-closing semiconductor switch. For positive voltages, it is activated by a high-voltage pulse at its cathode, and, when turned on, the current through the device rises rapidly. Using Synopsys TCAD software, a p+−n−n+ diode is numerically studied. It was shown that for the case of a high-doped active n region, 1014 cm−3, the breakdown process exhibits a fast electric field propagation, as expected. For a low doped active n region, <1011 cm−3, the electric field spreads uniformly along the structure. For this case, we show that the rise time, of the order of 100 ps, is not limited by the active region thickness, allowing the use of a thicker substrate in order to increase the operating voltage. A p+−n−n+ diode was fabricated on a thick, 525 μm, float-zone n-type Si (100) substrate, with a resistivity of 104 Ω cm. The active region, n<1012 cm−3, was 517 μm. When a stack of five, 8 mm2, diodes was driven by an ∼100 kV, 2.26 ns rise time pulse, the output voltage was 46 kV with the rise time and rise rate per diode of 215 ps and 38.4 kV/ns, respectively. When a single, 4 mm2, diode was driven by a 14 kV, 1 ns rise time pulse, the output on a 50 Ω load was around 8 kV, 100 ps, with a rise rate of 57 kV/ns. These results exceed the present state-of-the-art diodes. Furthermore, the thick active region eliminates current fabrication process difficulties such as deep diffusion or thick epitaxial layers.