Molecular beam homoepitaxy of N-polar AlN: Enabling role of aluminum-assisted surface cleaning

Abstract

N-polar aluminum nitride (AlN) is an important building block for next-generation high-power radio frequency electronics. We report successful homoepitaxial growth of N-polar AlN by molecular beam epitaxy (MBE) on large-area, cost-effective N-polar AlN templates. Direct growth without any in situ surface cleaning leads to films with inverted Al polarity. It is found that Al-assisted cleaning before growth enables the epitaxial film to maintain N-polarity. The grown N-polar AlN epilayer with its smooth, pit-free surface duplicates the structural quality of the substrate, as evidenced by a clean and smooth growth interface with no noticeable extended defects generation. Near band-edge photoluminescence peaks are observed at room temperature on samples with MBE-grown layers but not on the bare AlN templates, implying the suppression of nonradiative recombination centers in the epitaxial N-polar AlN.

Micro- and Nanostructure Analysis of Vapor-Phase-Grown AlN on Face-to-Face Annealed Sputtered AlN/Nanopatterned Sapphire Substrate Templates

“… 36 , 38 , 39 Interestingly, universal IDB structures have been observed among FFA Sp-AlN, MOVPE-grown AlN, and molecular beam epitaxy-grown AlN on FFA Sp-AlN. 36 – 40 Hence, the marked difference in the IDB morphology between Samples MOH and HVC suggests that the type of NPSS modifies how oxygen is supplied from the sapphire and incorporated in FFA Sp-AlN.…”

CMOS-compatible photonic integrated circuits on thin-film ScAlN

“…This value is consistent with other sputterdeposited AlN films in the literature, 31,32 but larger than those grown using epitaxial growth methods, whose rocking curve FWHM is as small as 0.004 ○ . 33 Next, we characterize the second-order nonlinear (χ (2) ) optical response of ScAlN using a second-harmonic generation (SHG) confocal microscope. The inset in Fig.…”

Optimization of the process parameters for the AlN crystal growth in the PVT method through an improved numerical simulation considering partial pressure of gas phases

“…As a result, preparing large-size and high-quality bulk AlN single crystals has recently become an important research topic. Various methods have been tried to prepare AlN single crystals, including hydride vapor phase epitaxy (HVPE), 11 the ammonothermal method, 12 molecular beam epitaxy (MBE), 13 metal-organic chemical vapor deposition (MOCVD), 14 and physical vapor phase transport (PVT). 15,16 Among them, PVT is the most successful method for preparing high-quality and large-size AlN single crystals.…”