In0.52Al0.48As/InxGa1‐xAs(x=0.53 lattice‐matched, andx=0.6 pseudomorphic) high electron mobility transistor (HEMT) structures are grown by a Riber‐32P MBE system on (100) InP:Fe substrates. Devices with the gate‐length of 0.8μm show excellent channel pinch‐off characteristics fromthe Ids‐Vdscurves. The saturation current density biased atVgs=0.5V is 480 mA/mm for HEMTs(x=0.53) and 550 mA/ mm for pseudomorphic‐(PHEMTs,x=0.6). A peak extrinsic DC transconductance (gm) increases from 342 mS/mm to 395 mS/mm as the In composition increases from 53% to 60% for In0.52Al0–48As/ InxGa1‐xAs HEMTs. Microwave characteristics demonstrate that a current gain cutoff frequency (fT) also increases from 22 GHz to 25 GHz and a maximum oscillation frequency (fmax) increases from 60 GHz to 83 GHz, at 300K. This demonstrates that with the increase of In content in InxGa1‐xAs channels, device performance is dramatically enhanced, which can be used for microwave circuit applications.