Measurement and analysis of internal loss and injection efficiency for continuous-wave blue semipolar (202¯1¯) III-nitride laser diodes with chemically assisted ion beam etched facets

Abstract

Continuous-wave blue semipolar $(20\overline{2}\overline{1})$ III-nitride laser diodes were fabricated with highly vertical, smooth, and uniform mirror facets produced by chemically assisted ion beam etching. Uniform mirror facets are a requirement for accurate experimental determination of internal laser parameters, including internal loss and injection efficiency, which were determined to be 9 cm⁻¹ and 73%, respectively, using the cavity length dependent method. The cavity length of the uncoated devices was varied from 900 μm to 1800 μm, with threshold current densities ranging from 3 kA/cm² to 9 kA/cm² and threshold voltages ranging from 5.5 V to 7 V. The experimentally determined internal loss was found to be in good agreement with a calculated value of 9.5 cm⁻¹ using a 1D mode solver. The loss in each layer was calculated and in light of the analysis several modifications to the laser design are proposed.