THEORY OF OPTICAL GAIN IN IDEAL GAN HETEROSTRUCTURE LASERS

We present gain calculations for ideal bulk GaN and 100 Angstrom GaN q uantum well laser structures. We show that due to the large electron a nd hole effective masses in GaN, the room-temperature material gain ch aracteristics of a 100 Angstrom quantum well are a little different fr om those of bulk GaN up to a gain level of 1000 cm(-1), and that the t ransparency and threshold carrier density is approximately 2.5 times t hat in an equivalent GaAs structure, with the radiative current densit y being of order eight times larger. Comparing the unstrained zinc ble nde and wurtzite crystal structures, we predict improved gain characte ristics in the wurtzite case. The introduction of compressive strain, e.g., through pseudomorphic growth between unstrained AlGaN barriers, will benefit both crystal structures, with wurtzite remaining better t han zinc blende for mismatch up to about 1.5%. Finally, we note that t he gain characteristics would be further improved if it were possible to grow tensile-strained zinc blende layers. (C) 1995 American Institu te of Physics.