Suppression of electron and hole overflow in GaN-based near-ultraviolet laser diodes

In order to suppress the electron leakage to p-type region of near-ultraviolet GaN/In_xGa_1-xN/GaN multiple-quantum-well (MQW) laser diode (LD), the Al composition of inserted p-type Al_xGa_1-xN electron blocking layer (EBL) is optimized in an effective way, but which could only partially enhance the performance of LD. Here, due to the relatively shallow GaN/In_0.04Ga_0.96N/GaN quantum well, the hole leakage to n-type region is considered in the ultraviolet LD. To reduce the hole leakage, a 10-nm n-type Al_xGa_1-xN hole blocking layer (HBL) is inserted between n-type waveguide and the first quantum barrier, and the effect of Al composition of Al_xGa_1-xN HBL on LD performance is studied. Numerical simulations by the LASTIP reveal that when an appropriate Al composition of Al_xGa_1-xN HBL is chosen, both electron leakage and hole leakage can be reduced dramatically, leading to a lower threshold current and higher output power of LD.