Title :
Self-aligned AlGaAs/GaAs HBT with low emitter resistance utilizing InGaAs cap layer
Author :
Nagata, Koichi ; Nakajima, Osaake ; Yamauchi, Yoshiki ; Nittono, Takumi ; Ito, Hiroshi ; Ishibashi, Tadao
Author_Institution :
Electr. Commun. Labs., NTT, Kanagawa, Japan
fDate :
1/1/1988 12:00:00 AM
Abstract :
A self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) with an InGaAs emitter cap layer that has very low emitter resistance is described. In this structure, a nonalloyed emitter contact allows the emitter and base electrodes to be formed simultaneously and in a self-aligned manner. The reduction of emitter resistance greatly improves the HBT´s transconductance and cutoff frequency. In fabricated devices with emitter dimensions of 2 μm×5 μm, a transconductance-per-unit-area of 16 mS/μm2 and a cutoff frequency of 80 GHz were achieved. To investigate high-speed performance, a 21-stage ECL ring oscillator was fabricated using these devices. Propagation delay times as low as 5.5 ps/gate were obtained, demonstrating the effectiveness of this structure
Keywords :
III-V semiconductors; aluminium compounds; bipolar integrated circuits; bipolar transistors; emitter-coupled logic; gallium arsenide; indium compounds; 5.5 ps; 80 GHz; AlGaAs-GaAs; ECL ring oscillator; InGaAs emitter cap layer; cutoff frequency; heterojunction bipolar transistor; high-speed performance; low emitter resistance; nonalloyed emitter contact; propagation delay times; self-aligned HBT; transconductance; Contact resistance; Cutoff frequency; Electrodes; Epitaxial layers; Gallium arsenide; Heterojunction bipolar transistors; Indium gallium arsenide; Ohmic contacts; Ring oscillators; Transconductance;
Journal_Title :
Electron Devices, IEEE Transactions on
