Comparative optical study of GaAs1-xNx/GaAs and BxGa1-xAs/GaAs epilayers

Optical studies of GaAs_1-xN_x/GaAs and B_xGa_1-xAs/GaAs epilayers grown by metal organic chemical vapour deposition (MOCVD), with various nitrogen (N) and boron (B) compositions, have been achieved by photoluminescence spectroscopy (PL) as a function of the excitation density and the sample temperature (10-300 K). The experiments have shown that the GaAsN PL band emission presents a more significant red shift than the BGaAs emission. For the GaAsN a reduction of 110 meV/1%N is shown, but for the BGaAs the PL band emission shifts to the low-energy side by up to 2.5%. A more significant blue shift of the PL bands with increasing the excitation density has been observed for GaAsN compared to BGaAs epilayer structures. The temperature dependence of the PL peak energy has shown S-shaped behaviour for both structures, but the localisation effects are more important in GaAsN than in BGaAs. Based on these experimental results, it is shown that B incorporation does not cause large modification of the band structure in B_xGa_1-xAs alloys compared to pure GaAsN structures.