CHARACTERIZATION OF ULTRAHIGH-SPEED PSEUDOMORPHIC INGAAS ALGAAS INVERTED HIGH ELECTRON-MOBILITY TRANSISTORS

A detailed characterization of ultrahigh-speed pseudomorphic InGaAs/AlGaAs inverted high electron mobility transistors (pseudomorphic 1-HEMT's) is reported. Charge control analysis indicates that the pseudomorphic I-HEMT accomplishes improved transconductance (g(m)) 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-mu-m gate pseudomorphic I-HEMT's reported here exhibit superior DC and RF performances, i.e., maximum transconductance (g(m)max) of 565 mS/mm, cutoff frequency (f(T)) of 110 GHz and propagation delay times (tau(pd)'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 (tau(transit)) and the channel charging time (tau(channel)) in the pseudomorphic I-HEMT, which are significant factors in the ultrahigh-speed performance. Higher electron saturation velocity (upsilon(s):2.1 x 10(7)cm/s) and improved g(m) are considered to contribute to the reduction in tau(transit) and tau(channel).