A far infrared modulated photoluminescence (FIRM-PL) study of cyclotron resonance in a 2D electron gas in GaAs/AlxGa1-xAs heterojunctions

The new technique of far infrared modulated photoluminescence (FIRM-PL) has been used to study the properties of a high mobility 2D electron gas in a series of GaAs/AlGaAs heterojunctions. When the occupancy of the lowest Lan dau level is between 1 and 2 very large transfers of PL intensity are obser ved at the cyclotron resonance condition. The PL intensity is transferred f rom the E-0 line to E-1 corresponding to emission from the first two quanti zed electric subbands. A study of the power dependence of this signal allow s us to deduce that the relative recombination efficiencies of the two line s are around five orders of magnitude different in such structures. This di fference leads to a very high sensitivity of this technique for the observa tion of internal excitations within the electron system.