The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) onsapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). Itwas found that ELO GaN stripes be...The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) onsapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). Itwas found that ELO GaN stripes bent towards the SiNx mask in the direction perpendicular toseeding lines. Each side of GaN (0002) peak in DC-XRD rocking curves was a broad peak relatedwith the crystallographic tilt. This broad peak split into two peaks (denoted as A and B), and peak Bdisappeared gradually when the mask began to be removed by selective etching. Only narrowpeak A remained when the SiNx mask was removed completely. A model based on these resultshas been developed to show that there are two factors responsible for the crystallographic tilt: Oneis the non-uniformity elastic deformation caused by the interphase force between the ELO GaNlayer and the SiNx mask. The other is the plastic deformation, which is attributed to the change ofthe threading dislocations (TDs) from vertical in the window regions to the lateral in the regionsover the mask.展开更多
介绍了金属有机化学气相沉积(Metal-Organic Chemical Vapor Deposition,MOCVD)法横向外延过生长GaN薄膜的原理,阐述了该技术形成选择生长和减少GaN薄膜缺陷密度的机理。综述了该技术的发展历程以及最新进展。新型的横向外延过生长技术...介绍了金属有机化学气相沉积(Metal-Organic Chemical Vapor Deposition,MOCVD)法横向外延过生长GaN薄膜的原理,阐述了该技术形成选择生长和减少GaN薄膜缺陷密度的机理。综述了该技术的发展历程以及最新进展。新型的横向外延过生长技术大大简化了生长工艺以及降低了晶向倾斜。展开更多
This study focused on the evolution of growth front about AlN growth on nano-patterned sapphire substrate by metal-organic chemical vapor deposition.The substrate with concave cones was fabricated by nano-imprint lith...This study focused on the evolution of growth front about AlN growth on nano-patterned sapphire substrate by metal-organic chemical vapor deposition.The substrate with concave cones was fabricated by nano-imprint lithography and wet etching.Two samples with different epitaxy procedures were fabricated,manifesting as two-dimensional growth mode and three-dimensional growth mode,respectively.The results showed that growth temperature deeply influenced the growth modes and thus played a critical role in the coalescence of AlN.At a relatively high temperature,the AlN epilayer was progressively coalescence and the growth mode was two-dimensional.In this case,we found that the inclined semi-polar facets arising in the process of coalescence were{112^-1}type.But when decreasing the temperature,the{112^-2}semi-polar facets arose,leading to inverse pyramid morphology and obtaining the three-dimensional growth mode.The 3 D inverse pyramid AlN structure could be used for realizing 3 D semi-polar UV-LED or facet-controlled epitaxial lateral overgrowth of AlN.展开更多
We report the reduced-strain gallium-nitride （GaN） epitaxial growth on （0001） oriented sapphire by using quasiporous GaN template. A GaN film in thickness of about 1 μm was initially grown on a （0001） sapphire ...We report the reduced-strain gallium-nitride （GaN） epitaxial growth on （0001） oriented sapphire by using quasiporous GaN template. A GaN film in thickness of about 1 μm was initially grown on a （0001） sapphire substrate by molecular beam epitaxy. Then it was dealt by putting into 45% NaOH solution at 100℃ for lOmin. By this process a quasi-porous GaN film was formed. An epitaxial GaN layer was grown on the porous GaN layer at 1050℃ in the hydride vapour phase epitaxy reactor. The epitaxial layer grown on the porous GaN is found to have no cracks on the surface. That is much improved from many cracks on the surface of the GaN epitaxial layer grown on the sapphire as the same as on GaN buffer directly.展开更多
InGaN/GaN multiple quantum wells （MQWs） are grown on planar and maskless periodically grooved sapphires by metal organic vapour phase epitaxy （MOCVD）. High-resolution x-ray rocking curves and transmission electron...InGaN/GaN multiple quantum wells （MQWs） are grown on planar and maskless periodically grooved sapphires by metal organic vapour phase epitaxy （MOCVD）. High-resolution x-ray rocking curves and transmission electron microscopy （TEM） are adopted to characterize the film quality. Compared with the MQWs grown on planar sapphire, the sample grown on grooved sapphire shows better crystalline quality： a remarkable reduction of dislocation densities is achieved. Meanwhile, the MQWs grown on grooved sapphire show two times larger PL intensity at room temperature. Temperature-dependent PL measurements are adopted to investigate the luminescence properties. The luminescence thermal quenching based on a fit to the Arrhenius plot of the normalized integrated PL intensity over the measured temperature range suggests that the nonradiative recombination centres （NRCs） are greatly reduced for the sample grown on grooved sapphire. We assume that the reduction of dislocations which act as NRCs is the main reason for the sample grown on pattern sapphire having higher PL intensity.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 69825107), NSFC-RGC Joint Program (Grant Nos. NSFC5001161953 and N_HKU028/00).
文摘The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) onsapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). Itwas found that ELO GaN stripes bent towards the SiNx mask in the direction perpendicular toseeding lines. Each side of GaN (0002) peak in DC-XRD rocking curves was a broad peak relatedwith the crystallographic tilt. This broad peak split into two peaks (denoted as A and B), and peak Bdisappeared gradually when the mask began to be removed by selective etching. Only narrowpeak A remained when the SiNx mask was removed completely. A model based on these resultshas been developed to show that there are two factors responsible for the crystallographic tilt: Oneis the non-uniformity elastic deformation caused by the interphase force between the ELO GaNlayer and the SiNx mask. The other is the plastic deformation, which is attributed to the change ofthe threading dislocations (TDs) from vertical in the window regions to the lateral in the regionsover the mask.
文摘介绍了金属有机化学气相沉积(Metal-Organic Chemical Vapor Deposition,MOCVD)法横向外延过生长GaN薄膜的原理,阐述了该技术形成选择生长和减少GaN薄膜缺陷密度的机理。综述了该技术的发展历程以及最新进展。新型的横向外延过生长技术大大简化了生长工艺以及降低了晶向倾斜。
基金supported by the National Key R&D Program of China (No. 2016YFB0400800)the National Natural Sciences Foundation of China (Grant Nos. 61875187, 61527814, 61674147, U1505253)+1 种基金Beijing Nova Program Z181100006218 007Youth Innovation Promotion Association CAS 2017157
文摘This study focused on the evolution of growth front about AlN growth on nano-patterned sapphire substrate by metal-organic chemical vapor deposition.The substrate with concave cones was fabricated by nano-imprint lithography and wet etching.Two samples with different epitaxy procedures were fabricated,manifesting as two-dimensional growth mode and three-dimensional growth mode,respectively.The results showed that growth temperature deeply influenced the growth modes and thus played a critical role in the coalescence of AlN.At a relatively high temperature,the AlN epilayer was progressively coalescence and the growth mode was two-dimensional.In this case,we found that the inclined semi-polar facets arising in the process of coalescence were{112^-1}type.But when decreasing the temperature,the{112^-2}semi-polar facets arose,leading to inverse pyramid morphology and obtaining the three-dimensional growth mode.The 3 D inverse pyramid AlN structure could be used for realizing 3 D semi-polar UV-LED or facet-controlled epitaxial lateral overgrowth of AlN.
文摘We report the reduced-strain gallium-nitride （GaN） epitaxial growth on （0001） oriented sapphire by using quasiporous GaN template. A GaN film in thickness of about 1 μm was initially grown on a （0001） sapphire substrate by molecular beam epitaxy. Then it was dealt by putting into 45% NaOH solution at 100℃ for lOmin. By this process a quasi-porous GaN film was formed. An epitaxial GaN layer was grown on the porous GaN layer at 1050℃ in the hydride vapour phase epitaxy reactor. The epitaxial layer grown on the porous GaN is found to have no cracks on the surface. That is much improved from many cracks on the surface of the GaN epitaxial layer grown on the sapphire as the same as on GaN buffer directly.
基金Support by the National High Technology Research and Development Programme of China under Grant Nos 2001AA313120, the National Natural Science Foundation of China under Grant Nos 10474126 and 10574148, and the National Key Basic Research and Development Programme of China under Grant No 2002CB311900.
文摘InGaN/GaN multiple quantum wells （MQWs） are grown on planar and maskless periodically grooved sapphires by metal organic vapour phase epitaxy （MOCVD）. High-resolution x-ray rocking curves and transmission electron microscopy （TEM） are adopted to characterize the film quality. Compared with the MQWs grown on planar sapphire, the sample grown on grooved sapphire shows better crystalline quality： a remarkable reduction of dislocation densities is achieved. Meanwhile, the MQWs grown on grooved sapphire show two times larger PL intensity at room temperature. Temperature-dependent PL measurements are adopted to investigate the luminescence properties. The luminescence thermal quenching based on a fit to the Arrhenius plot of the normalized integrated PL intensity over the measured temperature range suggests that the nonradiative recombination centres （NRCs） are greatly reduced for the sample grown on grooved sapphire. We assume that the reduction of dislocations which act as NRCs is the main reason for the sample grown on pattern sapphire having higher PL intensity.
