Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH_3 interrupted etching

Abstract

Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching. Subsequently, a 2-µm-thick Si-doped a-GaN layer was regrown on the etched a-GaN layer. A fully coalescent n-type a-GaN layer with a low threading dislocation density (~7.5 × 10(8) cm(-2)) and a low basal stacking fault density (~1.8 × 10(5) cm(-1)) was obtained. Compared with a planar sample, the full width at half maximum of the (11-20) X-ray rocking curve was significantly decreased to 518 arcsec along the c-axis direction and 562 arcsec along the m-axis direction.

Selective area growth of GaN nanostructures: A key to produce high quality (11–20) a-plane pseudo-substrates

“…20,21 In addition, GaN nanostructures are strain free, so that the PL spectrum is not blue shifted. The presence of strong and dominant BSF-related emission in the PL spectrum is in contrast to what is observed in SAG GaN nanostructures grown on semi-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and polar (0001) templates. Indeed, in the semipolar case an efficient filtering of BSFs from the underlying GaN template was observed.…”

“…Selective area growth of GaN nanostructures: A key to produce high quality (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane pseudo-substrates S. Albert, 1,a) A. Bengoechea-Encabo, 1,a) J. Zuniga-Perez, 2 P. de Mierry, 2 P. Val, 1 M. A. Sanchez-Garcia, 1 Selective area growth of GaN nanostructures was performed on (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane GaN/sapphire templates. The dominant lateral growth rate along the in-plane c-direction produces the coalescence of the individual nanostructures into a continuous film.…”

“…4 An alternative approach consists in using such defective layers as initial templates to grow thereon defect-free GaN nanostructures by selective area growth (SAG). SAG of GaN nanostructures has been demonstrated on c-plane GaN/sapphire templates 5,6 and more recently on non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane GaN templates 7 and semi-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN templates. 8 This work reports on the molecular beam epitaxy (MBE) SAG and characterization of isolated, partially and fully coalesced GaN nanostructures on (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane GaN/ sapphire templates with the aim to fabricate a coalesced layer of improved optical quality for further overgrowth by other techniques such as metalorganic chemical vapor deposition (MOCVD).…”

“…The molecular fluxes were calibrated in (0001) GaN growth rate units (nm/ min). 9 SAG was performed using a nanohole Ti mask fabricated by colloidal lithography on a MOCVD non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) GaN/sapphire template. Details on the mask preparation can be found elsewhere.…”

“…7 At this point, it has to be noted that the high roughness may even facilitate the fabrication of high quality templates by further overgrowth since the irregular and rough surface can effectively bend threading dislocations and prevent their propagation. 11 In order to evaluate the quality improvement of the non-polar SAG GaN nanostructures upon SAG before coalescence, LT-PL spectra shown in Figure 2 were taken of sample A1 and the a-plane GaN template (prior to growth).…”