MICROWAVE PERFORMANCE OF TOP-COLLECTOR CHARGE INJECTION TRANSISTORS ON INP SUBSTRATES

Charge injection transistors have been implemented in molecular beam e pitaxy grown InGaAs/InAlAs/InGaAs and InGaAs/InP/InGaAs heterostructur es using a self-aligned process for the collector stripe definition. S cattering parameters have been measured in the frequency range from 10 0 MHz to 40 GHz. InP barrier devices show the best microwave performan ce ever reported for a real-space transfer transistor at 40 GHz the sh ort circuit current gain \h21\ is 8 dB and the power gain is larger th an unity. The slope of \h21(f)\ depends on the bias point and is gener ally gentler than 20 dB decade-1. Extrapolating at the measured slope, we find \h21\ = 1 at f = 115 GHz. The short circuit current gain cut- off f(T), defined by extrapolation at 20 dB decade-1 from the point of least mean square deviation of the measured slope from 20 dB decade-1 , is f(T) = 73 GHz. Devices with InAlAs barriers show a relatively slo wer performance (f(T) = 32 GHz). The difference is discussed in terms of the relative rates of intervalley scattering and real-space transfe r in the two heterostructures.