Output light power of InGaN-based violet laser diodes improved by using a u-InGaN/GaN/AlGaN multiple upper waveguide

The upper waveguide (UWG) has direct influences on the optical and electrical characteristics of the violet laser diode (LD) by changing the optical field distribution or barrier of the electron blocking layer (EBL). In this study, a series of InGaN-based violet LDs with different UWGs are investigated systematically with LASTIP software. It is found that the output light power (OLP) under an injecting current of 120 mA or the threshold current (I_th) is deteriorated when the UWG is u-In_0.02Ga_0.98N/GaN or u-In_0.02Ga_0.98N/Al_xGa_1-xN (0 ≤ x ≤ 0.1), which should be attributed to small optical confinement factor (OCF) or severe electron leakage. Therefore, a new violet LD structure with u-In_0.02Ga_0.98N/GaN/Al_0.05Ga_0.95N multiple layer UWG is proposed to reduce the optical loss and increase the barrier of EBL. Finally, the output light power under an injecting current of 120 mA is improved to 176.4 mW.