Heterojunction bipolar transistor with base layer having graded

Details Heterojunction bipolar transistor with base layer having graded Heterojunction bipolar transistor with base layer having graded

1993-08-04

1994-12-06

Larkins, William D.

Active solid-state devices (e.g., transistors, solid-state diode

Heterojunction device

Bipolar transistor

257198, 257592, H01L 29161, H01L 29205, H01L 29225

Patent

active

053713893

ABSTRACT:
A base layer interposed between an n-type GaAs collector layer and an n-type AlGaAs emitter layer is composed of a p-type InAlGaAs. From a collector/base interface to an emitter/base interface, an InAs composition of the base layer is decreased and a concentration of carbon as a p-type impurity thereof is increased so as to obtain a built-in internal field intensity in the base layer by a cooperative effect of the graded-bandgap and the impurity concentration gradient, thus reducing a base transit time of electrons. The base layer is fabricated according to MOMBE using TMG as a gallium source, controlling the InAs composition, so that a desired carbon concentration gradient is automatically formed. Thereby, a high performance heterojunction bipolar transistor with an increased built-in internal field intensity in the base layer is obtained.

REFERENCES:
patent: 4482910 (1984-11-01), Nishizawa et al.
O. Nakajima et al., "Supression of Emitter Size Effect on Current Gain in AlGaAs/GaAs HBTs", Japan J. Applied Phys., vol. 24, No. 10, pp. 1368-1369 (1985).
S. Nozaki et al., "GaAs Pseudo-Heterojunction Bipolar Transistor With a Heavily Carbon-Doped Base", Extended Abstracts of the 1991 International Conference on Solid State Devices and Materials, pp.356-358.

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