Heterojunction bipolar transistor

US4933732A · kind A · utility

Assignee

• Kabushiki Kaisha Toshiba · JP

Inventors

• Riichi Katoh · Yokohama, JP
• Mamoru Kurata · Tokyo, JP
• Kouhei Morizuka · Yokohama, JP

Key dates

• Filing date: Jun 30, 1988
• Grant date: Jun 12, 1990
• Expiry date: Jun 30, 2008

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D10/821

Abstract

A heterojunction bipolar transistor comprises a first semiconductor layer of a first conductivity type, a second semiconductor layer of the first conductivity type formed on the first semiconductor layer, a third semiconductor layer of a second conductivity type formed on the second semiconductor layer, the first, second and third semiconductor layers serving as a collector, a fourth semiconductor layer of the second conductivity type formed on the third semiconductor layer, the fourth semiconductor layer serving as a base, and a fifth semiconductor layer of the first conductivity type formed on the fourth semiconductor layer, the fifth semiconductor layer serving as an emitter, the fourth and fifth semiconductor layers together forming a heterojunction, and the fifth semiconductor layer having a larger band gap than the fourth semiconductor layer, wherein the first, second, third and fourth semiconductor layers are related as follows: ##EQU1## where N.sub.1, N.sub.2, N.sub.3, and N.sub.4 are impurity concentrations of the first, second, third, and fourth semiconductor layers, respectively, e is the unit charge, .epsilon. is the dielectric constant of the collector, V.sub.bi is the…