InP-based high-electron mobility transistor (HEMT) structures have been grown containing strained In1-xAlxP Schottky layers with x=0.15-0.25. The band gaps of the strained layers in the HEMT structure were determined by photoreflectance spectroscopy. For x=0.15, Hall mobilities were comparable to those obtained in an analogous InAlAs/InGaAs structure. Lower mobilities were obtained with higher x value. Misfit dislocations were observed in plan view transmission electron microscopy for x=0.25 but not x=0.15. HEMT structures were also grown with InAsP channel layers containing moderate sheet densities. Photoluminescence measurements of the quantum well region indicated transitions to two electronic subbands. The InAs1-xPx composition was found to be weakly dependent on the phosphorus flux and uniform on 2 in. wafers.