We have investigated the use of lattice-matched AlxGa1-xSbAs quaternary alloys in InP-based microelectronic devices. The band alignment for AlxGa1-xSbAs/InGaAs is calculated across the entire compositional range of x using van de Walle and Martin's model solid theory, and the theoretical predictions agree with previously published values within 0.1-0.3 eV. Temperature-dependent current-voltage measurements are carried out on Au/Cr/AlxGa1-xSbAs Schottky diodes grown by molecular beam epitaxy. From an Arrhenius analysis, an effective barrier height of 0.67-0.79 eV is obtained, which decreases as the x increases in the range of 0.5 less than or equal tox less than or equal to0.9. For the first time. InAlAs/InGaAs high electron mobility transistors are fabricated with an AlxGa1-xSbAs barrier enhancement layer. A reduced gate leakage and delay of gate forward turn-on are attributed to the incorporation of AlxGa1-xSbAs. The effectiveness of AlxGa1-xSbAs is more pronounced for x = 0.5 and 0.7 than for x = 0.9.