We observe a significant increase in InSb quantum-well mobility when remote doping of Al0.09In0.91Sb barriers is accomplished by three layers, rather than one layer, of Si delta doping. At 7 K, the electron mobility in single quantum-well structures grown on GaAs substrates is as high as 280 000 cm(2)/V s with an electron density of 2.33 x 10(11) cm(-2). The density of oriented abrupt steps and square-mound features on the sample surface correlates with the electron mobility in the well.