Experimental Study on Displacement Damage Effects of Anode-Short MOS-Controlled Thyristor

Abstract

The metal-oxide-silicon (MOS)-controlled thyristor (MCT) has been characterized by MOS-gating, high-current-rise rate, and high blocking capabilities. The anode-short MCT (AS-MCT) is distinguished from conventional MCT by an anode-short structure, which forms an extracting path for electron current at the gate ground and develops a normally-off characteristic. As a composite structure made of MOS and bipolar junction transistors, AS-MCT is susceptible to displacement damage (DD). For the first time, this article reports the DD effects on AS-MCT with the fast neutron flux in the range of 3.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> - 5.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . Both the transfer and forward conductive characteristics are degraded subsequent to neutron exposures. When the neutron flux surpasses a critical value, the function failure of AS-MCT occurs, i.e., the AS-MCT cannot be latched up and enter into the thyristor-like conductivity mode, and, instead, remains in the insulated gate bipolar transistor-like conductivity mode. For the forward blocking characteristics (open gate), both the anode leakage current and forward blocking voltage increase subsequent to neutron exposures. To note, a novel phenomenon is observed for AS-MCT following neutron exposures, i.e., the forward current-voltage curve exhibiting “double snap-back effect.” This article proposes, from a device physics perspective, the mechanism behind the characteristics of degradation from DD in AS-MCT. The dependencies of the key parameters on neutron flux and the failure neutron flux are analytically modeled. Our models provide an excellent fit to the experimental data of the XND1 AS-MCT subjected to fission neutrons.