Internal Optical Waveguide Loss and p-Type Absorption in Blue and Green InGaN Quantum Well Laser Diodes

We present a new characterization method for internal optical waveguide loss of blue, aquamarine, and green group-III–nitride laser diodes from as-grown wafers without need for further fabrication. This approach relies on excitation-position dependent polarization-resolved photoluminescence spectra collected from the edge of the planar waveguide. The high measurement accuracy of ±1 cm -1 enables for the first time determination of the mechanisms for p-layer optical loss from the waveguide loss difference before and after Mg dopant activation. Temperature-dependent measurements show that the dominant optical loss mechanism is absorption by acceptor-bound holes. This absorption mechanism does not depend significantly on light polarization.