Characterization of Ultrahigh-Speed Pseudomorphic InGaAs/AlGaAs Inverted High Electron Mobility Transistors

Abstract

A detailed characterization of ultrahigh-speed pseudomorphic InGaAs/AlGaAs inverted high electron mobility transistors (pseudomorphic I-HEMT's) is reported. Charge control analysis indicates that the pseudomorphic I-HEMT accomplishes improved transconductance (gm) and reduced short channel effects due to higher concentration and excellent confinement of two-dimensional electron gas (2DEG) in the InGaAs channel. The 0.2 µm gate pseudomorphic I-HEMT's reported here exhibit superior DC and RF performances, i.e., maximum transconductance (gmmax) of 565 mS/mm, cutoff frequency (fT) of 110 GHz and propagation delay times (τpd's) of 6.6 ps/gate at R.T. and 4.9 ps/gate at 120 K. Delay time analysis reveals the reduction of both the electron transit time (τtransit) and the channel charging time (τchannel) in the pseudomorphic I-HEMT, which are significant factors in the ultrahigh-speed performance. Higher electron saturation velocity (υs:2.1×107 cm/s) and improved gm are considered to contribute to the reduction in τtransit and τchannel.