Characterization of microwave transistors

Abstract The design, fabrication and evaluation of double-diffused, epitaxial silicon bipolar microwave transistors are discussed. The design approach is intended to maximize the transducer G T = ¦s fe ¦ 2 , MAG and unilateral U power gains. Shallow impurity profiles ( x E = 2000−3000 A , x C = 3000−4000 A ) and narrow emitter strips (h = 1.5−2.0 μm) provide typical current-gain bandwidth width products fT's > 4 GHz and maximum frequencies of oscillation fMAX's > 6 GHz. The electrical performance of the microwave transistor is described by the s-(scattering) parameters which are derived from the T-small-signal equivalent circuit in terms of the physical device parameters. The behavior of the s-parameters vs. frequency for the common-emitter amplifier is predicted and verified experimentally in the frequency range from 1.0 to 6.0 GHz. The physics of the microwave transistor operation is discussed and the fabrication of double-diffused, epitaxial silicon transistors is presented.