Microwave performance of top-collector charge injection transistors on InP substrates

Abstract

Charge injection transistors have been implemented in molecular beam epitaxy grown InGaAs/InAlAs/InGaAs and InGaAs/InP/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 mod h21 mod is 8 dB and the power gain is larger than unity. The slope of mod h21(f) mod depends on the bias point and is generally gentler than 20 dB decade-1. Extrapolating at the measured slope, we find mod h21 mod =1 at f=115 GHz. The short circuit current gain cut-off fT, 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 fT=73 GHz. Devices with InA/As barriers show a relatively slower performance (fT=32 GHz). The difference is discussed in terms of the relative rates of intervalley scattering and real-space transfer in the two heterostructures.