Ultra-low-power SiGe HBT technology for wide-range microwave applications

Ultra-low power SiGe HBT was developed for wide-range microwave applications. The key technologies of the SiGe HBT are based on well-controlled SiGe / Si epitaxial growth techniques with low-temperature chemical vapor deposition (CVD), which give several important features of the low-power SiGe HBT. The prominent features are a robustly designed n
⁺
-n
^-
-p
⁺
emitter-base junction and a narrow base, realized by an epitaxially grown emitter and a low-temperature thermal cleaning prior to the emitter growth. These features were found to decrease both an emitter junction capacitance (C
_JE
) and a carrier transit time in base (tau
_B
) in a great extent. The low-temperature CVD also contributed to the reduction of a collector junction capacitance (C
_JC
) by controlling a mono-poly interface in the collector. The effective decrease of C
_JE
, tau
_B
, and C
_JC
has increased a cutoff frequency (f
_T
) at a wide range of a collector current density (J
_C
). As a result, Jc of the SiGe HBT decreased more than 60% compared to published data, at a wide f
_T
range from 30 to 200 GHz.