Abstract
AbstractThe hetero‐epitaxy of () GaN on () sapphire was optimized in metal–organic vapor phase epitaxy. Best results were obtained from an AlN nucleation followed by AlN and AlGaN layers, and inserting low‐temperature AlN interlayers (ILs) as well as a SiNx IL. X‐ray diffraction (XRD) of scans of the symmetric () reflection yielded an FWHM along [] and along [] together with a m rms roughness below 10 nm as determined by atomic force microscopy. The lowest threading dislocation density achieved was cm while the basal plane stacking fault density was in the lower cm range as determined by transmission electron microscopy. The suppression of the unwanted () phase was lower than 1 in 10,000 as judged from XRD.
Highlights
With its reduced spontaneous and piezoelectric fields, the semi-polar (112 ̄2) GaN is promising for the fabrication of green and yellow light-emitting diodes and normally-off field effect transistors
4 Conclusions We have investigated and evaluated several metal–organic vapor phase epitaxy (MOVPE) growth methods to obtain (112 ̄2) GaN templates hetero-epitaxially grown on sapphire substrates
The method using AlN nucleation at higher temperatures, followed by a graded AlGaN layer and thermal annealing allowed for very smooth GaN layers at a relatively thin total layer thickness
Summary
With its reduced spontaneous and piezoelectric fields, the semi-polar (112 ̄2) GaN is promising for the fabrication of green and yellow light-emitting diodes and normally-off field effect transistors. The (112 ̄2) orientation can be obtained by GaN epitaxy on m-plane (101 ̄0). Such templates have typically a huge density of dislocations in the 1010 cm−2 range and basal-plane stacking faults (BSFs) in the upper 105 cm−1 range [1,2,3]. Contributions from the unwanted (101 ̄3 ̄) phase have been observed [4, 5]. It has been shown that by inducing three dimensional (3D) growth, the peak width in X-ray diffraction (XRD) can be strongly reduced [2].
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