Structural characterization and elastic strain of InGaN/GaN multiple quantum wells

X-ray diffraction, transmission electron microscopy and Rutherford backscattering/channeling are used to characterize the structure of an InGaN/GaN multiple quantum well (MQW) grown on an Al₂O₃(0001) substrate. Using the combination of these measurements, not only the layered structure of the MQW is revealed clearly but also the In content x (0.16) of the In_xGa_1-N component can be determined reliably, which is a prerequisite for further determination of the elastic strain of the MQW. X-ray θ-2θ scans of the (0002) and (101~4) diffractions are used to determine the average lattice parameters epi> and epi> of the MQW, consequently the average parallel elastic strain 11> = -0.25% and the average perpendicular elastic strain ⊥> = +0.13% of the MQW are deduced. The experimental result of ⊥>/11> = -0.52 is in good agreement with the value deduced from the elastic constants.