Semipolar III-Nitride laser diodes for solid-state lighting

摘要

Several hurdles to further enhance the performance of semipolar III-Nitride laser diodes are addressed in this work.Particularly, we focused on improving their high operating voltage by thinning the p-GaN cladding layer and utilizing atransparent conductive oxide p-contact. On-wafer optical absorption measurements showed that a further reduction involtage with thinner p-GaN was limited by increased optical loss due to increased mode overlap with the ITO/metalanode. In separate attempts to minimize bulk-related optical losses, we implemented a new design that consisted of anAlGaN electron blocking layer (EBL) placed remotely from the quantum wells (QWs) and a low p-waveguide Mgdoping profile. A very low optical loss of about 2 cm~(-1) was extracted but the net improvement in differential efficiencywas limited by lower internal injection efficiency due to carrier accumulation in the p-waveguide region. With anoptimized design, that consisted of a lightly doped EBL close to the QWs and a UID p-waveguide, an improved lightoutput power of 1.4 W at 1.5 A and a low threshold current density of 1.2 kA/cm~2 were obtained.