Determination of the phase of magneto-intersubband scattering oscillations in heterojunctions and quantum wells

The oscillatory magnetoresistance of a two-dimensional electron system with two occupied subbands has been studied in an ${\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ heterojunction and an ${\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}{\mathrm{A}\mathrm{s}/\mathrm{I}\mathrm{n}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ quantum well between 4 and 100 K. As a consequence of the second populated subband, a magneto-intersubband scattering effect is observed at low-magnetic fields in addition to the Shubnikov–de Haas effect. Due to the different temperature damping of the two effects, the oscillatory magnetoresistance can exhibit both effects simultaneously at high and respectively low fields. Using the extrema positions, it is possible to clearly identify a theoretically predicted phase difference between the Shubnikov–de Haas and the magneto-intersubband scattering oscillations at temperatures higher than 4 K. This phase difference influences the power spectrum of reciprocal-field magnetoresistance data.