CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

Abstract

We have studied crystal structure and associated defects in GaN films grown on sapphire under nitrogen-deficient conditions by metalorganic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD). The structural quality of the PLD films grown at 750 0 C was comparable with those grown by MOCVD at 1050 0 C having threading dislocations density of about 10 10 cm -2 at a film thickness 150-200 nm. Microstructure of the PLD films grown at temperatures above 780 0 C was found to be similar to that of nitrogen-deficient MOCVD films indicating the loss of nitrogen due to thermal decomposition of the nitride layers. Nitrogen-deficient MOCVD and PLD films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. Most of the stoichiometric films displayed (0001) Ga-face polarity, but the renucleated inclined wurtzite grains grew in the opposite N-face polarity. The major defects related to the cubic structural metastability are stacking faults and microtwins which being nuclei of the metastable cubic phase have an extremely low energy. We elucidate that the cubic phase is more stable under the nitrogen deficiency and, therefore, can exist without decomposition at higher nitrogen vacancy concentrations in the material.

Ammonothermal Conversion of Cyclotrigallazane to GaN: Synthesis of Nanocrystalline and Cubic GaN from [H2GaNH2]3

“…The electron diffraction patterns of the crystallites exhibited streaking of the diffraction spots perpendicular to the close-packed planes; also consistent with a structure containing numerous defects such as stacking faults. While these striations could also be described as micro-twinning, 38 the electron diffraction data and the presence of peaks attributable to both the cubic and hexagonal phases in the X-ray diffraction pattern suggest a disordered structure containing stacking faults.…”

Structural study of gallium oxynitrides prepared by ammonolysis of different oxide precursors

“…However, we have shown that gallium oxynitride, prepared by ammonolysis of a nickel gallate precursor, has a complex structure, which could be considered as a polytype where two arrangements of cubic (zinc-blende) and hexagonal (wurtzite) structures may coexist [8,18]. The mixing of the two structures has been observed in GaN thin films [13][14][15][16] but, to our knowledge, such a result has not been reported elsewhere for gallium oxynitride powders. While the crystal structures of zinc-blende and wurtzite are very similar [12], their lattice vibrations are different.…”

“…GaN is known to be highly stable in the hexagonal wurtzite structure [12], but the growth of the cubic (zinc-blende) phase has also been reported in thin films [13][14][15][16]. Zincblende-wurtzite polytypism is well known in semiconductors.…”

Chemical Vapor Deposition of β-LiGaO2Films on Si(100) Using a Novel Single Precursor

“…In other words, Ga-terminated films would grow on the (001) plane of LiGaO 2 that has a cationterminated surface, 5 16 All the chemicals and solvents were purified and dried by standard methods described in the literature. 17 The 1 H and 13 C NMR spectra were recorded on a Bruker DPX 300 MHz spectrometer with chemical shifts referenced internally to benzene-d 6 . FTIR spectra were recorded on a Nicolet Magna-IR 550 spectrometer as a Nujol mull between KBr plates.…”