Title :
Design study of passivation ledge in AlGaAs/GaAs heterojunction bipolar transistors
Author_Institution :
Dept. of Electron. Eng., Nat. Yunlin Inst. of Technol., Taiwan
Abstract :
A thin AlGaAs passivation ledge on the extrinsic base surfaces of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is widely used to reduce the extrinsic base surface recombination current and increase the common emitter current gain. However, the design of the ledge and its effectiveness on base current reduction need to be further investigated. In this paper, HBTs with different ledge structures are analyzed with 2-dimensional simulation. The results indicate that a thinner ledge provides better suppression of electron lateral (horizontal) diffusion in the base, and therefore reduces the electron component in base current. Optimization of the ledge design and GaAs surface passivation process is essential for device reliability, too. A new device structure with heavily doped extrinsic base layers is proposed to further improve the base current
Keywords :
III-V semiconductors; aluminium compounds; gallium arsenide; heavily doped semiconductors; heterojunction bipolar transistors; passivation; semiconductor device reliability; surface recombination; 2-dimensional simulation; 2D simulation; AlGaAs; AlGaAs-GaAs; GaAs surface passivation process; HBT; base current; common emitter current gain; device reliability; electron lateral diffusion supression; extrinsic base surfaces; heavily doped extrinsic base layers; heterojunction bipolar transistors; ledge design optimisation; passivation ledge; surface recombination current reduction; thin AlGaAs passivation ledge; Bipolar transistors; Capacitance; Circuit noise; Electrons; Gallium arsenide; Heterojunction bipolar transistors; Logic circuits; Passivation; Spontaneous emission; Voltage;
Conference_Titel :
Microelectronics and VLSI, 1995. TENCON '95., IEEE Region 10 International Conference on
Print_ISBN :
0-7803-2624-5
DOI :
10.1109/TENCON.1995.496351
