Effect of Morphological and Structural Properties on SIMS Depth Profiles of InGaN/GaN Multiple Quantum Wells Grown on Sapphire by MOCVD

Abstract

InGaN/GaN multiple quantum well (MQW) structures have been grown by metalorganic chemical vapor deposition on c-plane sapphire substrates. Inverted diamond-like surface defects (i.e., V-pits) with a density of [Formula: see text][Formula: see text]cm[Formula: see text] have been observed in an eight-QW structure with Ga[Formula: see text]In[Formula: see text]N (3.6[Formula: see text]nm thick) and GaN (12.7[Formula: see text]nm thick) as the well- and barrier-material, respectively. The density of the surface defects has been significantly decreased by simply reducing the well-width to 2.7[Formula: see text]nm while keeping the other structural parameters nominally intact. The decrement in the well-width caused remarkable changes in depth profiles of In/Ga probed by secondary ion mass spectroscopy (SIMS) from the MQW structures, which is related to the varied effects of cratering roughness and accumulative interface roughness. The SIMS depth profiles also revealed increased In incorporations and QW-period in the QWs near the top surface for the MQW structure with larger well-width. They are most likely associated with surface defects, accumulative interface roughness, and strain evolutions along the growth direction.