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 I-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 μm 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 (τ_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 (τ_transit) and the channel charging time (τ_channel) in the pseudomorphic I-HEMT, which are significant factors in the ultrahigh-speed performance. Higher electron saturation velocity (\upsilon_s:2.1× 10⁷ cm/s) and improved g_m are considered to contribute to the reduction in τ_transit and τ_channel.