On the Investigation of Degradation Mechanisms in Ultra-High Performance Gaas Heterojunction Bipolar Transistors

Summary form only given. Recently, current-induced degradation in the form of V/sub BE/ shifts has been reported when the heterojunction is stressed under high-level forward current injection. Although the V/sub BE/ shift is an indication of device parameter change, the degradation mechanisms cannot be readily identified. An approach is presented that uncovers the device degradation mechanisms by measuring the inverted mode I/sub C/ at room temperature and the forward mode I/sub B/ at low temperature. The correlation between the change in the inverted I/sub C/ and an anomalous component (tunneling current) of I/sub B/ is observed and attributed to beryllium interstitial diffusion into substitutional sites. >