Investigation of photoelectric performance of laser diode by regulation of p-waveguide layer thickness

It is important to design semiconductor laser diode with a broad waveguide layer structure by simulation in theory for achieving high output power and high power conversion efficiency. The influence of p-waveguide layer thickness on the optical and electrical properties was studied by theoretical calculation and experimental results. Optical field distribution results indicated that transverse electric (TE) modes of the optical field mainly distribute in waveguide layer and fractional photons leaked into the cladding layer which result in increasing the optical loss. The maximum value of internal quantum efficiency was obtained when the p-waveguide layer thickness was 550 nm and its physical mechanism was revealed by boundary current density of quantum well and sheet electron and hole concentration in the active region. Moreover, the increasing band offset of p-waveguide layer could result in a decrease of the leakage current which can be explained by energy band theory. Finally, the optimal output power and photo-electronic conversion efficiency were obtained with 550 nm p-waveguide layer. The relationship among these photo-electronic parameters was analyzed, which will be favorable for designing semiconductor laser structure and providing a theoretical basis for growing high power semiconductor laser. Experimentally, a single chip with 2000 μm cavity length and 20% fill factor was fabricated, realizing a high power laser that agrees well with the theoretical results.