The Metal Base Transistors

Abstract

One of the major challenges in modern microelectronics is the creation of microwave devices or very high speed logic switches working in the 100 GHz range. It is now clear that device performances are no more limited by the transit time of the carriers in the active region of the structures. For instance, a p-n-p transistor with a 1 µm base width could in principle, operate in the 100 GHz range (for a saturation velocity of 10⁷ cm/sec as in most common semiconductors) while the best results obtained in Si, using a super self-aligned technology (S.S.T.), are in the 20 GHz range [1]. This limitation is clearly due to the R_accC_p time constant of the device, R_acc being the access resistance and C_p the parasitic capacitance of the device.