Abstract: A high mobility p channel semiconductor device (such as a field-effect transistor) is 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 5 nm wide and very deep quantum wells (about 0.4 eV and deeper) to reduce the effective mass of "heavy" conduction holes for motion in the plane of the quantum well. 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. In a particular example such a quantum well is formed of GaAs (or GaInAs) between AlAs barrier layers.