In this thesis we have investigated impurities profiles in a semiconductor layers,rnusing Monte Carlo simulation technique in an external parabolic potential. By ignoringrnimpurity - impurity Coulombâ€™s interaction, first we considered impuritiesrndiffusion in the presence of external parabolic potential that has minimum at therncenter of the semiconductor at a different temperatures. The model was modifiedrnand included the impurity impurity Coulombâ€™s interaction. Using Arrhenius typernequation, we have performed Monte Carlo simulation to predict impurities profilernfor different amplitudes of external parabolic potential, temperatures and impuritiesrndensity per sites. When we approximated the non - linear potential as onerndimensional parabola which has a minimum at the mid point of the semiconductorrnlayer, the impurity is accumulated in the central region. Our results show thatrnthe external potential has influenced the diffusion towards the center even thoughrnan internal potential has opposite effect. Moreover the impurity distribution has arnGaussian profiles that becomes sharper when the amplitude of external parabolicrnpotential is increased. Our simulation results were compared with the pervious relatedrnworks. The variation of the gaussian width within a temperature and dopantrndensity per site were also observed that as the temperature increases the plots becomesrnbroaden. Similarly, as the dopant density per site at the initial increases thernimpurities per site around the center of the graph becomes higher and broaden.