We have grown high quality AlGaAs/GaAs heterostructures by GSMBE, using triethylalkyls and arsine, for MODFET device applications. Al.28Ga.72As/GaAs modulation-doped structures with moblilities as high as 7,200 and 47,000 cm2/V-s at 300 and 77K, respectively, were obtained for a spacer layer thickness of 30Å and a sheet carrier concentration of l×l012cm−2. These results are comparable to films of a similar structure grown by elemental source MBE or by OMVPE techniques. Quarter-micron gate length MODFETs fabricated from this material have fr greater than 38 GHz and exhibit a 1.7 dB noise figure with 10 dB associated gain at 18 GHz when operated at room temperature.