CYCLOTRON-RESONANCE IN ULTRA-LOW-HOLE-DENSITY NARROW P-TYPE GAAS (AL,GA)AS QUANTUM-WELLS/

The cyclotron-resonance behavior of a series of p-type, low p(s), asym metrically doped (311)A quantum wells has been measured over two order s of magnitude in energy. Landau levels for the structures studied hav e been calculated for comparison with experiment. The calculations use a rotated Luttinger Hamiltonian and invoke the axial approximation. I n the quantum limit and at certain far-infrared energies we observe tw o resonances widely separated in field. We find at the lowest fields t hat the samples exhibit a light effective mass. For the narrowest quan tum well the cyclotron resonance (CR) broadens and shifts to a slightl y lighter mass into the quantum limit, above about 2 T. The CR energy is modeled by inter-landau-level transitions from the highest level, a nd a discontinuous evolution to a higher effective mass, observed as t he second resonance above 8 T, is explained by crossing of the highest two Landau levels, as modeled in the calculation. The discontinuous e volution to a higher mass is found to shift to lower fields as the wel l width increases, as suggested from the modeling. For the wider quant um wells the influence of additional anticrossings at intermediate fie lds, due to the proximity of the second subband, is observed. CR energ y for these samples is adequately modeled at energies above and below the region of subband anticrossing. The limitations of the modeling pr ocedure have been discussed and a number of features of the experiment al data are explained qualitatively in terms of the expected modificat ions to the hole Landau-level structure when full Landau-level mixing is incorporated into the modeling. The influence of hole-hole interact ions and factors influencing the CR scattering time are also discussed briefly.