Al0.3Ga0.7As/In0.15Ga0.85As doped-channel structures were grown by molecular beam epitaxy on 3'' GaAs substrates. The uniformities of electrical and optical properties across a 3'' wafer were evaluated. A maximum 10% variation of sheet charge density and Hall mobility was achieved for this doped-channel structure. A 1 mum long gate field-effect transistor (FET) built on this layer demonstrated a peak transconductance of 350 mS/mm with a current density of 470 mA/mm. Compared to the high electron mobility transistors, this doped-channel FET provides a higher current density and higher breakdown voltage, which is very suitable for high-power microwave device applications.