Effect of emitter contact materials on high-performance vertical p-n-p transistors

Ion-implant doped polysilicon, in situ doped polysilicon, and in situ doped ultrahigh vacuum chemical vapor deposition (UHV/CVD) low-temperature epitaxial silicon emitter contacts were used to fabricate shallow junction vertical p-n-p transistors. The effect of these materials on emitter junction depth and on device characteristics is reported. A DC current gain as high as 45 was measured on polysilicon emitter devices. Regardless of emitter contact material, all devices showed sufficiently high breakdown voltages for circuit applications. However, only for ion-implant doped polysilicon emitter devices was the narrow-emitter effect observed through the emitter-collector punchthrough voltage, emitter resistance, and current gain measurements.<>