Atomic force microscopy analysis of cleaved facets in Ⅲ-nitride laser diodes grown on free-standing GaN substrates

摘要

The cleaved {1100} mirror facets of Ⅲ-nitride ridge waveguide laser diodes grown on free-standing GaN substrates have been characterized using atomic force microscopy. The measurements indicate that the exposed facets are atomically smooth and therefore they have a much lower roughness than has been reported for cleaved surfaces of Ⅲ-nitride heterostructures grown on other substrates. Individual heterostructure layers—including InGaN quantum wells only 3 nm thick—could be identified from small variations in the height of the exposed surface. These variations are attributed primarily to the partial relaxation of strained layers at the free surface.