Bulk AlN growth by physical vapour transport

Abstract

The process technologies of AlN growth by physical vapour transport are reviewed in this paper with a focus on the growth parameters, crucible materials, and the type of seeding/nucleation. In this context the three growth strategies for the first generation of AlN seeds, (i) grain selection, (ii) heteroepitaxially seeding on SiC, and (iii) spontaneous nucleation, are evaluated regarding their impact on the structural properties and the sizes of the grown AlN crystals. Major issues for subsequent homoepitaxial growth runs with controlled diameter enlargement, such as thermal field design and seed fixation, are addressed. Furthermore, the influences of the growth conditions on the main optical absorption bands in AlN are discussed.

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

“…[33] Although there are still challenges, such as contamination from impurities, lack of large-sized AlN seeds, and difficulty in tailoring desired thermal profile inside the growth reactor that hinder the reproducible growth to cite a few, [34] several groups have achieved PVT-grown AlN single crystals with diameters up to 2 inch. [32,[35][36][37][38][39] X-ray rocking curves with a full width at half maximum (FWHM) close to 30 arcsec for both (0002) and (101 2) reflections and etch pit densities (EPDs) below 10 4 cm -2 were reported with an usable area of ~85%. [32] Low dislocation density AlGaN epilayers with both symmetric and asymmetric rocking curves below 100 arcsec have been grown on these AlN wafers.…”

“…The underlying mechanisms for the formation of these bands are still under discussion. [35,39,[44][45][46][47][48][49][50] Specifically, at least three absorption bands at 2.8 eV, 3.3-4.3 eV and 4.7 eV were found and discussed for PVT-grown AlN. The origin of the 2.8 eV band is still an issue of intense debate.…”

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

“…Although there are still challenges, such as contamination from impurities, lack of large-sized AlN seeds, and difficulty in tailoring desired thermal profile inside the growth reactor that hinder reproducible growth to cite a few [37], several groups have achieved PVT-grown AlN single crystals with diameters up to 2 inch [35,[38][39][40][41][42]. X-ray rocking curves with a full width at half maximum (FWHM) close to 30 arcsec for both (0002) and (1012) reflections and etch pit densities (EPDs) below 10 4 cm −2 were reported with an usable area of~85% [35].…”

“…These absorption bands are attributed to residual impurities such as silicon, oxygen (mainly from the source materials), and carbon (mainly from the reactor parts such as TaC crucible) and intrinsic point defects, and Al vacancies. The underlying mechanisms for the formation of these bands are still under discussion [38,42,[47][48][49][50][51][52][53].…”

Effects of phosphoric acid on the surface morphology and reflectance of AlN grown by MBE under Al-rich conditions

“…Native AlN substrates are commercially available [4]; however AlN growth on substrates larger than two inches in diameter currently requires use of a foreign substrate such as sapphire, silicon or silicon carbide. A range of growth techniques have been reported for fabrication of high quality epitaxial AlN films on foreign substrates.…”