ABSTRACT
The effect of input flow rates on the morphology of < https://www.w3.org/1998/Math/MathML"> 1010 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063100/ce4a879a-688a-4c77-a95b-e9b91ed32a4e/content/inline-math120.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> >-oriented GaN stripes prepared by lateral epitaxial overgrowth (LEO) is investigated, and their optical and structural properties are analyzed using a combination of photoluminescence (PL) spectroscopy, cathodoluminescence (CL) imaging, and x-ray diffraction. The LEO GaN was grown by low pressure metalorganic chemical vapor deposition on 2 μm thick GaN/Al2O3 substrates covered with a SiO2 layer in which stripe openings were etched. In this stripe orientation the LEO morphology appears to be mainly determined by the V/III ratio in the gas phase: a low V/III ratio favors the { https://www.w3.org/1998/Math/MathML"> 11 2 ¯ 2 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063100/ce4a879a-688a-4c77-a95b-e9b91ed32a4e/content/inline-math121.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> } facets, while a moderate and high V/III ratio favors the { https://www.w3.org/1998/Math/MathML"> 11 2 ¯ 0 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063100/ce4a879a-688a-4c77-a95b-e9b91ed32a4e/content/inline-math122.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> } and { https://www.w3.org/1998/Math/MathML"> 10 1 ¯ 1 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063100/ce4a879a-688a-4c77-a95b-e9b91ed32a4e/content/inline-math123.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> } facets, respectively. We propose that this is related to the ratio of the number of Ga and N dangling bonds on the various facets. The CL imaging and time-integrated PL confirmed that the luminescence intensity is enhanced in the low-dislocation density material; however the time-resolved PL signals suggest that the basic emission mechanisms are essentially unaffected by threading dislocations.
