Effect of base dopants on the bias stress stability of AlGaAs/GaAs HBTs

The effect of three base dopants C, Be and Zn on the bias stress stability of npn AlGaAs/GaAs HBTs has been investigated for the first time. In this study 3*30 mu m² HBTs were fabricated under identical process technology, emitter-base geometry and layout design. Following 24 h of identical bias stress, it is found that both Be- and Zn-doped devices exhibited current gain degradation as high as 68 and 57%, respectively, compared with only 7% for the C-doped device. The superior bias stress stability of C-doped HBTs is demonstrated.