A high mobility p channel semiconductor device (such as a field-effect transistor) is formed suitable for operation at room temperature, for example in a circuit with an n channel device. Whereas hole modulation doping both in single heterojunction and in heterostructure quantum well devices provides a significant increase in hole mobility only at cryogenic temperatures, the present invention employs less than 5nm wide and very deep quantum wells 1 (about 0.4 eV and deeper) to reduce the effective mass of "heavy" conduction holes for motion in the plane of the quantum well 1. Hole mobilities at 300 degrees K are obtained in excess of 2.5 times those in bulk material of the same narrow bandgap semiconductor as used for the quantum well 1. In a particular example such a quantum well 1 is formed of GaAs (or GaInAs) between AlAs barrier layers 2.