| Heterostructure FET's based on InAlAs/InGaAs and GaInP/GaAs materials were fabricated and systematically studied for high speed integrated circuit applications. The performance of different HEMT and HIGFET designs was evaluated and compared. InAlAs/InGaAs and GaInP/GaAs materials demonstrate some promising features which make them very attractive for replacing the most commonly used AlGaAs/GaAs system. Strained channel designs can improve the transport properties of both n- and p-channel FET's by reducing the carrier effective mass and improving the carrier confinement.;Unlike the AlGaAs/GaAs HEMT's, GaInP/GaAs HEMT's show no current collapse or threshold voltage shift at low temperature. This indicates minimum trapping effects in the doped GaInP layer as confirmed by low-frequency noise measurements; pure 1/f noise was found at low temperature without Lorentz-shaped spectra.;Strained InAlAs/InGaAs p-doped channel designs demonstrated a performance improvement compared to the lattice-matched case due to the reduction of the hole effective mass. P-channel HIGFET's realized by Carbon and Argon co-implantation presented a lower access resistance compared to the conventional Be-implantation, and resulted in a better g;Lattice-matched and strained InAlAs/In;E/D-mode InAlAs/InGaAs HIGFET's circuits demonstrated a high uniformity of threshold voltage, high DC gain, large noise margin and high thermal stability. Functional logic gates based on the E/D-mode HIGFET can be operated at least up to 400 MHz, and the switching time for a single inverter stage was found to be as low as 25 psec. |
