The work reported in this paper examines another alternative offered by Al0.52In0.48P/InyGa1-yAs. This new pseudomorphic HEMT design offers: (i) a larger ΔEc(0.45eV) than pseudomorphic Al0.22Ga0.78As/InyGa1-yAs(0.36eV) with the same channel (y=0.2) composition and thus better confinement, (ii) reduction of DX-center related problems and (iii) high etching selectivity between GAAs/InGaAs and AlInP and thus improved threshold voltage uniformity due to better gate recess control. This paper presents for the first time the DC and microwave characteristics of submicron(0.1μm) gate-length Al0.52In0. 48P/In0.2Ga0.8As HEMT's grown by Gas Source Molecular-Beam Epitaxy (GSMBE).