EFFECTIVE-MASS ANISOTROPY IN GAAS-(GA,AL)AS 2-DIMENSIONAL HOLE SYSTEMS - COMPARISON OF THEORY AND VERY HIGH-HELD CYCLOTRON-RESONANCE EXPERIMENTS

Cyclotron resonance of two-dimensional holes in high-mobility GaAs-(Ga , Al)As heterojunctions with the growth directions [011], [111], [211] , [311] and [100] has been measured at magnetic fields of around 35 T, corresponding to Landau level occupancies deep in the ultraquantum li mit. A manipulation of the standard four-band Luttinger Hamiltonian ha s been used to show that the behaviour of the hole ground state is dom inated by the leading held-dependent term in a power series expansion for the Landau level dispersion. The experimentally observed trend in measured effective mass with substrate orientation can therefore be qu alitatively explained in terms of the variation of bulk hole mass with crystallographic direction.