Bipolar transistor with an improved collector structure

US5336909A · kind A · utility

Assignee

• Kabushiki Kaisha Toshiba · JP

Inventors

• Riichi Katoh · Yokohama, JP
• Kunio Tsuda · Ishikawa, JP

Key dates

• Filing date: Aug 14, 1992
• Grant date: Aug 9, 1994
• Expiry date: Aug 14, 2012

Classification

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

Abstract

In a very high speed bipolar transistor, an n.sup.+ -type GaAs collector layer and an n-type GaAs collector layer are stacked in an intrinsic transistor region, and an i-type GaAs collector layer is formed around the n.sup.+ -type GaAs collector layer and the n-type GaAs collector layer. An n-type GaAs collector layer is formed on the n.sup.+ -type GaAs collector layer such that a part of the n-type GaAs collector layer extends on the i-type GaAs collector layer. A p-type GaAs external base layer is formed outside the n-type GaAs collector layer. A p.sup.+ -type Al.sub.x Ga.sub.l-x As base layer is formed on the n-type GaAs collector layer. An emitter layer is formed such that it is arranged only in the intrinsic transistor region on the p.sup.+ -type Al.sub.x Ga.sub.l-x As base layer and constitutes a heterojunction together with the base layer. Design trade-off between the cutoff frequency and maximum oscillation frequency of the transistor is eliminated.