Defect reduction in (112¯2) semipolar GaN grown on m-plane sapphire using ScN interlayers

Abstract

The effect of ScN interlayer thickness on the defect density of (112¯2) semipolar GaN grown on m-plane sapphire was studied by transmission electron microscopy. The interlayers comprised Sc metal deposited on a GaN seedlayer that was nitrided before GaN overgrowth by metal-organic vapor-phase epitaxy. Both interlayer thicknesses reduced the dislocation density by a factor of 100 to low-108 cm−2. The 8.5 nm interlayer produced regions that were free from basal plane stacking faults (BSF) and dislocations. The overall BSF density here was reduced by a factor of 5, to (6.49±0.07)×104 cm−1, without the need for an ex situ mask patterning step.

Comparative study of polar and semipolar (112¯2) InGaN layers grown by metalorganic vapour phase epitaxy

“…22,23 For semipolar ð11 22Þ nitrides (e.g., InN, 23,26 GaN, 7 and AlGaN 27 ), the XRC FWHM value was found to be larger along ½1 100 than along ½ 1 123 . Figure 3 shows the on-axis XRC FWHM values measured along both in-plane directions of the ð11 22Þ InGaN layers.…”

“…The MOVPE growth of the ð11 22Þ GaN templates is reported elsewhere, 19 with samples exhibiting typical threading dislocation and BSF densities of (3.0 6 0.2) Â 10 10 cm À2 and (3.2 6 0.3) Â 10 5 cm À1 , respectively. 7 InGaN layers were also simultaneously grown on (0001) GaN templates for comparison. The (0001) GaN templates were grown on high temperature AlN templates that were deposited on c-plane sapphire.…”

“…The anisotropic crystallinity (the full-width at half maximum (FWHM) values of the on-axis XRD rocking curves (XRC)) of semi-/non-polar nitrides is commonly observed, 7,22,23,26,27 and it is mainly due to the anisotropic growth and the unequal distribution of dislocations. 22,23 For semipolar ð11 22Þ nitrides (e.g., InN, 23,26 GaN, 7 and AlGaN 27 ), the XRC FWHM value was found to be larger along ½1 100 than along ½ 1 123 .…”

“…1 The reduction of PEs increases overlap between electron and hole wave-functions resulting in an increase of radiative recombination probability, which may overcome the "green gap" problem as well as enhance the performance of LEDs based on semi-polar nitrides. 2,3 Efficient green and yellow semipolar ð11 22Þ InGaN single quantum-well LEDs grown on free-standing ð11 22Þ GaN substrates with threading dislocation densities below 10 7 cm À2 have been recently demonstrated. 4,5 However, the free-standing GaN substrates required for this approach remain small and expensive.…”

“…However, a major disadvantage of the latter approach is the potentially detrimental contribution of high defect densities of threading dislocations (typically %10 10 cm À2 ) and basal plane stacking faults (BSFs) (%10 5 cm À1 ). 6,7 It has been shown that the high density of BSFs affects the optical and electrical properties of the layers, e.g., increasing the nonradiative recombination rate 8 and causing an electrical anisotropy via the carrier scattering from BSFs. 9 It is particularly interesting regarding the application for green and yellow light emitters that an increased indium incorporation on the ð11 22Þ surface was predicted from firstprinciples calculations by Northrup,10 who argued that the strain-repulsive interaction between In-atoms in GaN is weaker on the ð11 22Þ surface than on the nonpolar ð10 10Þ m-plane surface.…”