Title :
Anomalous current gain degradation in bipolar transistors
Author :
Nitsu, Y. ; Yamaura, Kazuaki ; Momose, Hiroshi ; Maeguchi, Kenji
Author_Institution :
Toshiba Corp., Kawasaki, Japan
Abstract :
The current gain of a bipolar transistor, h/sub FE/, is degraded by the emitter-base reverse-bias stress. The mechanism has been interpreted to be due to an increase in the interface state density, while its dependence on stress time has been found to be proportional to t/sup n/, where n is 0.5 to 1. It was expected that if the stress time was long enough, the increase in interface state density would saturate to a maximum value. However, an anomalous time dependence of base current increase-a slower increase initially followed by a rapid increase in the intermediate stage-was found for bipolar transistors whose junction surface was oxidized in dry ambient conditions. This is explained by the hypothesis that the potential distribution is modulated by the charge in the oxide or at the interface.<>
Keywords :
bipolar transistors; electronic density of states; interface electron states; semiconductor device models; anomalous time dependence; base current increase; bipolar transistors; current gain degradation; dry ambient conditions; emitter-base reverse-bias stress; interface state density; junction surface oxidation; modulated potential distribution; oxide charge; stress time; trapped charges; Bipolar transistors; Circuits; Degradation; Interface states; Laboratories; Propagation delay; Ring oscillators; Semiconductor devices; Silicon; Stress;
Conference_Titel :
Reliability Physics Symposium, 1991, 29th Annual Proceedings., International
Conference_Location :
Las Vegas, NV, USA
Print_ISBN :
0-87942-680-2
DOI :
10.1109/RELPHY.1991.146013