THE PRESSURE-DEPENDENCE OF THE EFFECTIVE MASS IN A GAAS/ALGAAS HETEROJUNCTION

Cyclotron resonance ed high magnetic field with radiation in the far infrared has been used to measure the pressure coefficient of the effective mass, dm*/dp, of a GaAs heterojunction at pressures up to 8 kbar. Pressure is known to reduce the carrier concentration n(s). In this experiment, persistent photoconductivity was used to vary n(s) for each pressure so that dm*/dp was measured for fixed n(s). Furthermore, the energy dependence of the effective mass was determined for each n(s) and p. We find that, within our experimental error of approximately 5%, dm*/dp for the heterojunction is equal to dm*/dp for bulk GaAs, independent of n(s). This is understood from a simple k . p model. Anomalously n(s)-dependent pressure coefficients were observed for some cyclotron energies, which we relate to anomalous cyclotron mass values, perturbed from their true values by a number of effects that complicate cyclotron resonance in two dimensions.