Avalanche breakdown characteristics of punchthrough diodes

A theoretical investigation of the avalanche breakdown characteristics of punchthrough diodes is carried out and a comparison made with the nonpunchthrough diodes. It is shown that the former have harder breakdown characteristics and a sharper knee for a given breakdown voltage. In addition, punchthrough diodes have a lower temperature coefficient of breakdown voltage, a lower space-charge resistance, a negligible sensitivity of breakdown voltage to resistivity striations in single crystal wafers, and breakdown due to avalanche mechanism up to lower breakdown voltages. Though these positive features suggest that punchthrough diodes are superior in performance to nonpunchthrough diodes for applications such as voltage regulators etc., the final assessment will depend on a more critical evaluation of the reliability against burn out and instability.