Title :
A study of the current transport in AlGaAs/GaAs HBTs with graded and setback layers
Author :
Ho, C.S. ; Chen, D.L. ; Kager, A. ; Liou, J.J.
Author_Institution :
Dept. of Electr. & Comput. Eng., Central Florida Univ., Orlando, FL, USA
Abstract :
The combined effects of graded and setback layers (W/sub G/ and W/sub I/) on the AlGaAs/GaAs heterojunction bipolar transistor (HBT) d.c. performance are investigated, and an analytical model which can describe the behavior of such HBTs is presented. The HBT base and collector currents accounting for the variation of the conduction and valence bands due to the presence of W/sub G/ and W/sub I/ are also calculated. It is shown that including W/sub G/ and W/sub I/ actually degrades the HBT current gain at low current levels. The current gain at high current levels, on the other hand, can be enhanced if W/sub I/=150 /spl Aring/ and 0/spl les/W/sub G//spl les/300 /spl Aring/ or W/sub I/=0 and 150 /spl Aring//spl les/W/sub G//spl les/300 /spl Aring/ are used. The model predictions compare favorably with results calculated from a numerical model.
Keywords :
III-V semiconductors; aluminium compounds; conduction bands; gallium arsenide; heterojunction bipolar transistors; semiconductor device models; valence bands; 0 to 300 angstrom; AlGaAs-GaAs; HBTs; analytical model; base currents; collector currents; conduction band; current gain; current transport; graded layers; setback layers; valence band; Analytical models; Degradation; Dielectrics; Doping; Electrons; Electrostatics; Gallium arsenide; Heterojunction bipolar transistors; Permittivity; Tunneling;
Conference_Titel :
Southcon/94. Conference Record
Conference_Location :
Orlando, FL, USA
Print_ISBN :
0-7803-9988-9
DOI :
10.1109/SOUTHC.1994.498111
