Structural and Optical Properties of Carbon-Doped AlN Substrates Grown by Hydride Vapor Phase Epitaxy Using AlN Substrates Prepared by Physical Vapor Transport

Abstract

Freestanding AlN substrates with various carbon (C) concentrations were prepared from C-doped thick layers grown by hydride vapor phase epitaxy (HVPE) on bulk AlN substrates prepared by physical vapor transport (PVT). The structural properties of the AlN substrates up to a C concentration of 3×1019 cm-3 were the same as those of the nominally undoped substrates, while the absorption coefficient α at 265 nm was increased by C doping from 6.6 to 97 cm-1, when C concentration changed from <2×1017 to 1×1019 cm-3, respectively. Photoluminescence (PL) below 4.0 eV also increased by C doping.

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…Growth of thick AlN films by HVPE on PVT AlN substrates is instrumental in greatly reducing the AlN contamination (see e.g. recent papers [155,156]) while preserving the high crystalline quality of the material. Experiments performed in Refs.…”

“…Experiments performed in Refs. [155,156] allowed to directly relate the absorption in the 4.9 eV band and a strong PL band near 3.9 eV with C concentration. Theoretical calculations placing the C N À acceptor state in AlN near E v +2 eV allowed to attribute the absorption band to C N À ionization and the PL band to the transition from the conduction band to the C N À state involving strong lattice relaxation [156].…”

Vacancy compensation and related donor-acceptor pair recombination in bulk AlN

“…Following these observations, Kumagai et al 4 and Nagashima et al 5 implemented the use of hydride vapor phase epitaxy (HVPE) to grow UV transparent thick AlN layers on bulk AlN substrates prepared by physical vapor transport (PVT). These HVPE layers exhibited carbon levels below 2 Â 10 17 cm À3 and an absorption coefficient below 10 cm À1 for the wavelength of 265 nm.…”

Epitaxial Growth of AlN on (0001) Sapphire: Assessment of HVPE Process by a Design of Experiments Approach

“…Different methods have been used to grow AlN with a low dislocation density such as physical vapor transport (PVT) [8], solution growth [9], thermal nitridation [10], metalorganic chemical vapor deposition (MOCVD) [11] and hydride (or halogen) vapor phase epitaxy (HVPE) [12,13]. The most successful methods to provide substrates of high structural quality are the PVT method [8] or a combination of PVT and HVPE methods [14,15]. They provide AlN substrates with low dislocation densities (<10 4 cm −2 ) able to be used for AlGaN-based deep UV light-emitting devices.…”

“…All the experiments described in Table 1 led to epitaxial growth on (0001) sapphire. No disorientation is observed and AlN presents its classical orientation AlN (0001)//sapphire (0001) and AlN //sapphire [11][12][13][14][15][16][17][18][19][20]. Cracks could be observed on the surface of some samples (see Table 2 for details).…”