Title :
Si/SiGe heterojunction bipolar transistor with graded gap SiGe base made by molecular beam epitaxy
Author :
Narozny, P. ; Hamacher, M. ; Dambkes, H. ; Kibbel, H. ; Kasper, E.
Author_Institution :
AEG Res. Center, Ulm, West Germany
Abstract :
Si/SiGe heterostructure bipolar transistors (HBT) were fabricated and compared to Si homojunction transistors with the same doping levels. Low-temperature Si-MBE was used to form the heterojunction and the homojunction layer sequences. One HBT structure has a graded-gap base layer, where the Ge fraction is 20% at the emitter side and linearly graded to 0% toward the collector side. This gives an average Ge content of 10% in the base and increases the critical thickness. The second HBT structure has a spike-doped S-base, sandwiched to low-doped SiGe layers. A strain selective etching technique was used to contact the thin base layer. Both HBT structures exhibit a higher current gain than the homojunction structure.<>
Keywords :
Ge-Si alloys; elemental semiconductors; heterojunction bipolar transistors; molecular beam epitaxial growth; semiconductor epitaxial layers; semiconductor junctions; semiconductor materials; semiconductor technology; silicon; HBT structures; MBE; Si homojunction transistors; Si-SiGe heterostructure bipolar transistors; critical thickness; current gain; doping levels; graded gap SiGe base; graded-gap base layer; molecular beam epitaxy; spike-doped S-base; strain selective etching technique; strained layer; Bipolar transistors; Capacitive sensors; Doping; Etching; Germanium silicon alloys; Heterojunction bipolar transistors; Molecular beam epitaxial growth; Photonic band gap; Silicon germanium; Temperature;
Conference_Titel :
Electron Devices Meeting, 1988. IEDM '88. Technical Digest., International
Conference_Location :
San Francisco, CA, USA
DOI :
10.1109/IEDM.1988.32877
