Microwave studies of self-aligned top-collector charge injection transistors

Charge injection transistors have been implemented in molecular-beam-epitaxy-grown lnGaAs/lnAlAs/lnGaAs and InGaAs/lnP/InGaAs heterostructures using a self-aligned process for the collector stripe definition. Scattering parameters have been measured in the frequency range from 100 MHz to 40 GHz. InP-barrier devices show the best microwave performance ever reported for a real-space transfer transistor: at 40 GHz the short circuit current gain |h/sub 21/| is 8 dB and the power gain is larger than unity. The slope of |h/sub 21/ (f)| depends on the bias point and is generally gentler than 20 dB/dec. Extrapolating at the measured slope, we find |h/sub 21/|=1 at f=115 GHz. The short circuit current gain cutoff f/sub T/, defined by extrapolation at 20 dB/dec from the point of least mean square deviation of the measured slope from 20 dB/dec is f/sub T/=73 GHz.<>