Microwave Studies of Self-Aligned Top-Collector Charge Injection Transistors

Charge injection transistors have been implemented in molecular-beam-epitaxy-grown InGaAs/InALAs/InGaAs and InGaAs/InPDnGaAs heterosuuctures using a selfaligned process for the collector stripe definition. Scattering parameters have been measmd in the frequency range from 100 MHz to 40 GHz. InP-banier devices show the best microwave performance ever reported for a real-space transfer transistor: at 40 GHz the short circuit current gain lh2l I is 8 dB and the power gain is larger than unity. The slope of lhZ1 (f ) I depends on the bias point and is generally gentler than 20 dB/dec. Extrapolating at the measured slope, we find lh21 I = 1 at f=115GHz. The short circuit current gain cutoff fT. defined by extrapolation at 20 dB/dec from the point of least mean square deviation of the measured slope from 20 dB/dec is fT = 73 GHz. KO I l a w l i