Effect of GaN substrate thickness on the optical field of InGaN lasers diodes

Abstract

In this work the influence of GaN substrate thickness on the near and far-field patterns of InGaN lasers structures is analyzed. In simulation a conventional separate confinement heterostructure of InGaN-MQW / GaN / AlGaN is considered. A fluctuating behavior is found, showing that for some values of the substrate thickness the near and far- field patterns can be optimized and there are critical values of the substrate thickness that produce the lowest values of the confinement factor and the higher values of the full wide half-maximum of the far field. It is also shown that by substituting the GaN contact layer by an AlxGa1-xN layer with a parabolic variation of the Al content it is possible to reduce the optical field leakage to substrate. Results indicated that properly choosing the thickness of the substrate and replacing the n-GaN contact layer by a graded-index (GRIN) AlxGa1-xN layer it is possible to improve both the confinement factor and Far field pattern in nitride lasers.