Full text loading...
Cross-sectional schemantic profiles of two type structures grown on Si(110) substrates in this study, (a) type I structure: direct growth of GaN on an AlN buffer layer without an AlN/GaN SLs interlayer, (b) type II structrue: GaN growth on an AlN buffer layer with an AlN/GaN SLs interlayer.
Optical microscope images of two 1.3-μm-thick GaN surfaces (a) without (type I structure) and (b) with (type II structure) an AlN/GaN SLs interlayer. Cracked and crack-free GaN surfaces are clearly observed.
ω-2θ scan spectra of GaN (0002) diffraction peaks measured by HRXRD from the type I and type II structure samples, showing the strain converting effect from a tensile to a compressive state in the GaN. The figure inset illustrates a cross-sectional SEM image showing the sample structure.
Micro-Raman spectra of the type II sample in Fig. 3 and a bulk GaN reference sample at room-temperature. Comparing to the E2 (high) peak position of the bulk GaN, a double E2 (high) peak feature from the type II sample shows the different strain states in the sample, supporting the interpretation of HRXRD results in Fig. 3.
Dependence of the strain in GaN films on the average Al composition of the thin AlN/GaN SLs interlayer. The average Al composition is simply calculated by the AlN and the GaN thicknesses in the SLs measured by HRXRD.
Article metrics loading...