Fabrication and optical pumping of laser cavities made by cleaving and wet chemical etching

We report on fabrication and characterization of cleaved laser facets and photoelectrochemically wet etched laser facets in III-Nitrides grown by MOVPE on c-plane sapphire. The roughness of the cleaved facets in the InGaN/GaN double heterostructure (DH) laser cavities with a 1000-angstroms-thick active region is ≈25 nm, while that of the wet etched GaN facets is ≈100 nm. A theoretical model is developed for the maximum allowable laser facet roughness, which yields a value of 18 nm for uncoated GaN and 22 nm for the uncoated DH. Optically pumped laser action at room temperature is demonstrated in the cleaved DH laser cavities. Above the incident threshold pumping power of 1.3 MW/cm², the differential quantum efficiency increases by a factor of 34, the emission linewidth decreases to 13.5 meV, and the output becomes highly TE polarized. Wet chemical etching a 1-mm-long laser cavity into the GaN homostructure is found to increase the differential quantum efficiency by a factor of 2.