Density and well width dependences of the effective mass of twodimensional holes in (100) GaAs quantum wells measured by cyclotron resonance at microwave frequencies

Cyclotron resonance at microwave frequencies is used to measure the band mass (m_b) of the two-dimensional holes (2DH's) in carbon-doped (100) GaAs/AlxGa1-xAs heterostructures. The measured m_b shows strong dependences on both the 2DH density(p) and the GaAs quantum well width (W). For a fixed W, in the density range (0.4x10^11 to 1.1x10^11 cm^-2) studied here, m_b increases with p, consistent with previous studies of the 2DHs on the (311)A surface. For a fixed p = 1.1x10^11 cm^-2, mb increases from 0.22 m_e at W = 10 nm to 0.50 m_e at W = 30 nm, and saturates around 0.51 m_e for W > 30 nm.