Improvement of slope efficiency of GaN-Based blue laser diodes by using asymmetric MQW and InxGa1-xN lower waveguide

Series of GaN-based blue laser diodes (LDs) with different InxGa1-xN quantum barrier (QB) and lower waveguide (LWG) layers are investigated by using the two-dimension simulator LASTIP. It is found that a decrease slope efficiency is resulted when the indium content of InxGa1-xN quantum barrier (QB) layers is higher than about 1%, which is caused by the significantly increase of electron leakage current due to the piezoelectric polarization effect in high indium content InxGa1-xN last QB (LQB) layer. Therefore, an asymmetric MQW with a thin thickness of LQB is designed to lower the piezoelectric polarization effect and to reduce the electron leakage current. Meanwhile, a new LD structure with high InxGa1-xN LWG is also proposed to further reduce the optical loss. The two ways are useful to improve the slope efficiency.