The geometry optimizations and electronic structure calculations were performed for graphene sheet doped with aluminium (Al) and nitrogen (N). The effect of doping has been examined by changing the concentrations of dopants from 2 % (one atom of the dopant in 50 host atoms) to 12 % (six dopant atoms in 50 host atoms). All the calculations have been performed by using the Burai Graphical user interface that used the Quantum Espresso code based on density functional theory, plane waves, and pseudo potentials. By Al and N doping, p-type and n-type doping are induced respectively in the graphene sheet. The results showed that the planar structure of the graphene sheet remains unaffected on doping. However, the electronic properties were changed from semimetal to semiconductor with an increasing number of dopants. These interesting results provide the possibility of tuning the bandgap of graphene as required and therefore extend its application in electronic devices.