Influence of the illumination on the subband structure and occupation in Al _x Ga_1-x N/GaN heterostructures

The subband structure and occupation in the triangular quantum well at Al _x Ga_1-x N/GaN heterointerfaces have been investigated by means of temperature dependent Shubnikov-de Haas (SdH) measurements at low temperatures and high magnetic fields under illumination. After the illumination of the heterostructures, the total two-dimensional electron gas concentration increases, and the SdH oscillation amplitudes are enhanced when there is no additional subband occupation. It is also found that the energy separation between the subbands decreases after the illumination. We suggest that the illumination decreases the electric field and thus weakens the quantum confinement of the triangular quantum well at Al _x Ga_1-x N/GaN heterointerfaces. The GaN layer is thought to be the primary contributor of the excited electrons by the illumination.