Charge conversion of nearly free and impurity bound magneto-trions immersed in 2D electron or hole gas with optically tunable concentration

We report collection of precise photoluminescence maps (emission intensity versus energy and magnetic field) of superior-quality two-dimensional hole gases. The maps reveal field evolution of both direct and cyclotron-assisted recombination lines attributed to various excitonic complexes, either moving nearly freely in the plane or bound to the acceptors placed inside or outside the quantum well. Under two-beam illumination (with photon energies below and above the band-gap in the barrier) we were able to control hole concentration (in the same well), and in particular to decrease it beyond the point of p- to n-type conversion. Our results demonstrate contrast between charge conversion of free and acceptor-bound positive trions resulting from the breaking of charge reflection symmetry by a fixed impurity.