Effect of carrier confinement on photoluminescence from modulation-doped AlxGa1-xN/GaN heterostructures

Photoluminescence (PL) of modulation-doped Al0.22Ga0.78N/GaN heterostructur es was investigated. The PL peak related to recombination between the two-d imensional electron gases (2DEG) and photoexcited holes is located at 3.448 eV at 40 K, which is 45 meV below the free excitons (FE) emission in GaN. The peak can be observed at temperatures as high as 80 K. The intensity of the 2DEG PL peak is enhanced significantly by incorporating a thin Al0.12Ga 0.88N layer into the GaN layer near the heterointerface to suppress the dif fusion of photoexcited holes. The energy separation of the 2DEG peak and th e GaN FE emission decreases with increasing temperature. Meanwhile, the 2DE G peak energy increases with increasing excitation intensity. These results are attributed to the screening effect of electrons on the bending of the conduction band at the heterointerface, which becomes stronger when tempera ture or excitation intensity is increased. (C) 2000 American Institute of P hysics. [S0003-6951(00)00606-9].