넓은 발광 스펙트럼의 응용을 위한 GaN 피라미드 꼭짓점 위에서의 선택적 결정 성장

Abstract

We report on the growth and characterization of three-dimensional randomly shaped InGaN/GaN structures selectively grown on the apex of GaN pyramids for the purpose of enlarging the emission spectral range. We found that the variation of shape and size of the three-dimensional GaN structures depends on the growth temperature and surface area for the selective growth under circumstance of an intentional turbulence of gas stream. The selectively grown GaN structures grown at 1020 ℃ have irregular shapes, while the samples grown at 1100 ℃ have rather uniform hexagon pyramidal shapes. Irregular-shaped GaN structures were also obtained on the apex of GaN pyramids when the SiO2 mask was removed to 1/10 of the total height of the underlying GaN pyramid. When only 1/5 of the SiO2 mask was removed, however, the selectively grown GaN structures had similar hexagon pyramidal shapes resembling the underlying GaN pyramids. The CL (cathodoluminescence) spectra of the InGaN layers grown on the randomly shaped GaN structures showed a wide emission spectral range from 388 to 433 nm due to the non-uniform thickness and spatially inhomogeneous indium composition of the InGaN layers. This new selective growth method might have a great potential for the application of non-phosphor white LEDs with more optimized growth conditions for the InGaN layers with high indium composition and optimum process of electrodes for electrical injection.