Nanocolumn InGaN/GaN quantum-well crystals on flat and pillared Si substrates with nitrified Ga as a buffer layer

Abstract

Nanocolumn InGaN/GaN quantum-well crystals were deposited on pillared and flat Si substrates. A unique flower structure was synthesized on the Si pillars. Vertically aligned nanocolumn crystals were uniformly deposited on the flat Si substrate. Raman spectra measurement shows the crystals are fully relaxed. Photoluminescence measurement indicates much stronger photoluminescence excited from the flower structure than that from the crystals on the flat Si substrate. Reflectivity measurement demonstrates much lower reflectivity of the flower structure than that of the crystals on the flat substrate. Laser scanning confocal microscopy measurement indicates clear vertical photoluminescence distributions of the flower structure. Optical microscopy images show that there is a horizontal photoluminescence distribution on the pillared Si substrate and the quantum-well flower structure emits much brighter light than the crystals on the flat Si substrate. The flower structure improves the surface geometrical structure and enhances the extraction efficiency much more than the crystals on the flat Si substrate.

GaN-based nitride semiconductor films deposited on nitrified HfO2/Si substrate by molecular beam epitaxy

“…The n-GaN and p-GaN are about 1200 and 450 nm, respectively. The GaN is not column crystal, which is different from our previous nanocolumn GaN crystals result of GaN on Si [1,2]. This may be that the nitrified HfO 2 /Si can decrease the diffusion barrier of the incoming Ga and thus enhance the lateral growth of GaN on the nitrified HfO 2 /Si.…”

“…This is different from our previous experimental results of the InGaN/GaN quantum well structure on Si substrate with GaN or AlN as buffer layers. In our previous experiments, we always got phase-separated thin InGaN layers [1,2]. The photoluminescence (PL) splits into two clear parts at low temperature.…”

“…In order to reduce the defects and strain, column crystal growth, patterned substrate, and lateral overgrowth were usually used to grow GaN on Si with appropriate buffer layers. In our previous investigations, good quality nanocolumn GaN crystals and high efficient light-emitting quantum well (QWs) on the column crystals have been deposited on the flat and patterned periodic Si substrates [1,2]. Although column crystal have good optical and electronic properties, it is difficult to integrate column GaN devices with Si microelectronics.…”

Various types of GaN/InGaN nanostructures grown by MOCVD on Si(111) substrate

“…1 Introduction GaN nanowires(NWs) are now of a great interest due to its significant potentional for electronic and optoelectronic devices [1][2][3][4]. Also it can be promising approach for growth on technologically difficult substrates, such as Si and non-polar sapphire [5,6]. In the case of Si substrate, the large lattice mismatch (17%) and thermal expansion mismatch (46%) between Si and GaN results in a high dislocation density in epitaxial GaN, wafer bowing and/or cracks in GaN epitaxial layer.…”