Growth of highly conductive Al-rich AlGaN:Si with low group-III vacancy concentration

Publisher Copyright: © 2021 Author(s).The impact of AlGaN growth conditions on AlGaN:Si resistivity and surface morphology has been investigated using metalorganic chemical vapor deposition. Growth parameters including growth temperature, growth rate, and trimethylindium (TMI) flow have been systematically studied to minimize the resistivity of AlGaN:Si. We observed a strong anticorrelation between AlGaN:Si conductivity and growth temperature, suggesting increased silicon donor compensation at elevated temperatures. Secondary ion mass spectrometry and positron annihilation spectroscopy ruled out compensation by common impurities or group-III monovacancies as a reason for the observed phenomenon, in contrast to theoretical predictions. The underlying reason for AlGaN:Si resistivity dependence on growth temperature is discussed based on the possibility of silicon acting as a DX center in Al0.65Ga0.35N at high growth temperatures. We also show remarkable enhancement of AlGaN:Si conductivity by introducing TMI flow during growth. A minimum resistivity of 7.5 m? cm was obtained for n-type Al0.65Ga0.35N, which is among the lowest reported resistivity for this composition.& nbsp;(c)& nbsp;2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).& nbsp;Peer reviewe

Origins of Electrical Compensation in Si-Doped HVPE GaN

We report positron lifetime and X-ray absorption spectroscopy results in Si-doped GaN crystals grown by the hydride vapor phase epitaxy. Pushing the Si doping to high concentrations leads to surprisingly strong compensation effects. Positron experiments show that the concentrations of Ga vacancies are not high enough to be efficient compensation centers. Other acceptor-like impurities are present in concentrations orders of magnitude lower than the Si content in the samples. X-ray absorption shows that the local environment of Si dopants in compensated samples is different from the fully activated case. Simulated spectra of X-ray absorption near edge structure strongly suggest that in compensated spectra Si is likely to have more Si atoms in the nearest local environment. Hence, autocompensation of Si dopants appears as a likely compensation mechanism at high Si contents GaN samples grown by HVPE. This article is protected by copyright. All rights reserved.Peer reviewe

Effect of atomic layer annealing in plasma-enhanced atomic layer deposition of aluminum nitride on silicon

The effect of adding an atomic layer annealing step to a plasma-enhanced atomic layer deposition process of aluminum nitride was investigated with commonly available materials. The refractive index, crystallinity, stoichiometry, and impurity concentrations were studied from films grown from trimethylaluminum and ammonia precursors at 300 ° C on Si(111) substrates. Additional energy provided by the atomic layer annealing step during each deposition cycle was found to enhance the crystallinity and stoichiometry and increase the refractive index and film density. A polycrystalline hexagonal film with a weak c-axis orientation was obtained on substrates with and without native oxide, which is promising for applications that require high quality films at low temperatures.</p