Effect of Boron Incorporation on Structural and Optical Properties of AlN Layers Grown by Metal‐Organic Vapor Phase Epitaxy

Abstract

To investigate the effect of boron (B) incorporation on the structural and optical properties of aluminum nitride (AlN) layers, B‐doped AlN layers without columnar structures are grown on c‐plane sapphire substrates with an AlN underlayer by metal‐organic vapor phase epitaxy. Triethylboron, trimethylaluminum, and ammonia are used as B, Al, and N precursors, respectively. The B‐doped AlN layers exhibit a homogeneous B concentration of 2.0 × 1021 cm−3 (≈2%) at the macroscale and microscale. However, most of the B atoms segregate in the AlN layer at the nanoscale and do not form BAlN alloys. As a result, high‐density dot‐shaped crystalline defects are induced in the layer. The dot‐shaped crystalline defects align along the true{11true2true¯3true} facets and form complex inclined defects with high‐density oxygen atoms. These defects result in much worse crystalline quality and optical emission property than those of conventional crystalline defects, e.g., threading dislocations and stacking faults. Therefore, further improvement in the crystalline quality of B‐doped AlN is important to understand the potential properties of BAlN alloy semiconductors.

Demonstration of single-phase wurtzite BAlN with over 20% boron content by metalorganic chemical vapor deposition

“…[1][2][3][4][5][6][7][8][9] However, at present many epitaxial challenges need to be addressed to achieve high quality and to increase the boron content while maintaining the wurtzite phase, such as phase separation, limited thin film thickness, and limited adatom diffusion length. [10][11][12][13][14][15] The boron content of the wurtzite BAlN alloys has been limited to less than 15% with a relatively small thickness of 100 nm, which greatly limits the device applications of the BAlN alloys. 1 In this Letter, we report on the growth of a 360 nm single-phase wurtzite BAlN thin film with the boron composition of 22% on an AlN/sapphire template by metalorganic chemical vapor deposition (MOCVD).…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…This can be attributed to the empirical fact that magnesium impurities do not incorporate well into AlN and its high-aluminum-content alloys because of the high energy required to activate dopants. In particular, a high density of compensating point defects can be generated in these materials [153,154] ; such defects include nitrogen vacancies (V N ) [155] , substitutional magnesium (Mg Ga )-V N complex and other defect complexes [156][157][158] , and magnesium interstitials [159,160] . Therefore, high-conductivity p-type aluminum-rich Al x Ga 1−x N films are difficult to obtain because of the low doping efficiency caused by the high activation energies of the acceptor dopant atoms.…”

Nanoscale compositional analysis of wurtzite BAlN thin film using atom probe tomography

“…10 XRD combined with secondary ion mass spectroscopy (SIMS) also provided a significant discrepancy in the B composition, which was attributed to the fact that most of the B formed possible B-related clusters instead of BAlN alloys. 11 This B segregation was substantiated by the compositional inhomogeneity of Al and N observed by scanning transmission electron microscopyelectron diffraction spectroscopy (STEM-EDS). 11 However, it was not possible to observe the B distribution in STEM-EDS due to the detection limit of the system.…”

“…9 Despite the tremendous potential of BAlN in future electronics, optics, and photonics, it is extremely challenging to achieve a high B content or high crystallinity wurtzite BAlN films with large thicknesses. 10,11 The B content in BAlN has been limited by the possible phase separations, the short diffusion length of B, and strong parasitic reactions within the reactor, which may require complex growth methods to address such as flow modulation epitaxy. 3,[12][13][14][15] A previous study has shown that BAlN with a 12% B content, grown by metal organic vapor phase epitaxy (MOVPE), had a single phase wurtzite structure that was limited within the first 10 nm of material.…”

“…The BAlN local stoichiometry and compositional homogeneity can be affected by inhomogeneous chemical distribution such as local segregations/clustering, 10 nanoscale disordered precipitates, 11 defect sites (dislocations and twins), 10,17 or the presence of impurities. 38,39 To address these issues, we have performed an in-depth analysis of the local composition of the BAlN films.…”