Optical gain and saturation behavior in homoepitaxially grown InGaN/GaN/AlGaN laser structures

Optical gain and losses in semiconductor laser epilayers are of profound importance in device optimization. We used both parameters to estimate the potential of InGaN/GaN/AlGaN epitaxial system to be used as a laser structure emitting in a blue region. The sample was grown homoepitaxially by MOVPE technique on high quality bulk GaN substrates obtained in high pressure growth process. These structures are characterized by very low dislocation density (around 105 cm–2). As a result the reduction of a nonradiative recombination is expected which is reflected in reduced excitation pump power and gain saturation processes described by means of saturation length and a product of the latter and a maximum modal gain. To determine gain value and its saturation behavior a variable stripe length method is used employing one dimensional amplifier model. Maximum gain value of 190 cm–1 together with internal losses of 15 cm–1 are determined for the studied structure. Low value of maximum saturation length of 320 um was found in our structures. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)