Oscillatory effective mass in the two-dimensional electron gas from Shubnikov-de Haas measurements

The effective mass in the two-dimensional electron gas of a delta-doped Inx Ga1-xAs HEMT structure from the variation of the amplitude of the Shubnikov -de Haas oscillations was determined; with the temperature from measurement s obtained as a function of the magnetic field and the gate voltage. The ef fective mass shows at intermediate magnetic fields an oscillatory behaviour , periodic with the filling factor and with maximum amplitude for even fact ors, Its relation to the oscillatory behaviour of the cyclotron effective m ass and the effective g factor is discussed. The effective mass increases w ith the electron density and the inversion of the magnetic field, (C) 1999 Elsevier Science Ltd. All rights reserved.