Pd/Ge/Ti/Pt and Pd/Ge/Pd/Ti/Au ohmic contacts to n-type InGaAs were investigated for applications to AlGaAs/GaAs HBT emitter ohmic contacts. In the Pd/Ge/Ti/Pt ohmic contact minimum specific contact resistivity of $3.7${ imes}$10^{-6}$</TEX> $Omega$$ extrm{cm}^2$ was achieved by rapid thermal annealing at $^400{circ}C$/10 sec. In the Pd/Ge/Ti/Au ohmic contact, minimum specific contact resistivity of $1.1${ imes}$10^{-6}$</TEX> $Omega$$ extrm{cm}^2$ was achieved by annealing at 40$0^{circ}C$/10 sec but the ohmic performance was degraded with increasing annealing temperature due to the reaction between the ohmic contact materials and the InGaAs substrate. However, non-spiking planar interface and relatively good ohmic contact (high-$10^{-6}$ /$Omega$$ extrm{cm}^2$) were maintained after annealing at $450^{circ}C$/10 sec. Therefore, these thermally stable ohmic contact systems are promising candidates for compound semiconductor devices. RF performance of the AlGaAs/GaAs HBT was also examined by employing the Pd/Ge/Ti/Pt and Pd/Ge/Pd/Ti/Au systems as emitter ohmic contacts. Cutoff frequencies were 63.5 ㎓ and 65.0 ㎓, respectively, and maximum oscillation frequencies were 50.5 ㎓ and 51.3 ㎓, respectively, indicating very successful high frequency operations.