Polarity inversion of AlN film grown on nitrided a-plane sapphire substrate with pulsed DC reactive sputtering

Abstract

ARTICLES YOU MAY BE INTERESTED INThe effect of oxygen partial pressure (P O 2 ) on polarity and crystalline quality of AlN films grown on nitrided a-plane sapphire substrates by pulsed direct current (DC) reactive sputtering was investigated as a fundamental study. The polarity inversion of AlN from nitrogen (c)-polarity to aluminum (+c)-polarity occurred during growth at a high P O 2 of 9.4×10 3 Pa owing to Al-O octahedral formation at the interface of nitrided layer and AlN sputtered film which reset the polarity of AlN. The top part of the 1300 nm-thick AlN film sputtered at the high P O 2 was polycrystallized. The crystalline quality was improved owing to the high kinetic energy of Al sputtered atom in the sputtering phenomena. Thinner AlN films were also fabricated at the high P O 2 to eliminate the polycrystallization. For the 200 nm-thick AlN film sputtered at the high P O 2 , the full width at half-maximum values of the AlN (0002) and (1012) X-ray diffraction rocking curves were 47 and 637 arcsec, respectively.

AlN formation by an Al/GaN substitution reaction

“…This could be because a certain amount of GaN non-uniformly dissolved in the AlN layer, as discussed in the next TEM observation section. The screw- and edge-type dislocations of the AlN layers were estimated from the XRC-FWHM 12 at various heat treatment temperature and holding time, which are summarized in Table 1 .

Figure 8 XRC-FWHM of AlN (0002) and AlN (10–12) after heat treatment of Al/GaN samples with various holding times of 0–3 h at temperatures of 1473–1673 K.

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“…The XRC-FWHM of AlN (10-12) decreased with increasing holding time. The XRC-FWHM values for GaN before heat treatment were in the range of 83-124 arcsec for GaN (0002) and 83-108 arcsec for GaN(10)(11)(12). Here, the XRC-FWHM values for the AlN obtained from the substitution method were quite large compared with the GaN substrate as a starting material.…”

“…AlN can be grown in two forms: film and bulk. AlN films have been fabricated by various methods, such as metal–organic vapour-phase epitaxy (MOVPE) 4 , 5 , hydride vapour phase epitaxy (HVPE) 6 , 7 , pulsed laser deposition (PLD) 8 , 9 , molecular beam epitaxy (MBE) 10 , 11 , or sputtering 12 , 13 , to improve its crystalline quality, surface area, growth rate, or lower its processing temperature. Annealing techniques have been demonstrated to improve the crystalline quality of AlN films 14 – 16 .…”

Monolayer MoS2 Enabled Single-Crystalline Growth of AlN on Si(100) Using Low-Temperature Helicon Sputtering

“…According to the azimuthal off-axis φ-scan, the internal stress in the AlN epitaxial film can be deduced from the differences between the lattice constants of the film and the bulk. The internal stress along c -axis of AlN films (σ c ) on MoS 2 /Si­(100) substrates relative to AlN bulk can be calculated by Where c film and c bulk are the c -axis lattice constants of the AlN epitaxial film and strain-free bulk AlN, respectively; and E is the Young’s modulus of AlN bulk ( E = 308 GPa). , From the 2θ–ω scan shown Figure a, the AlN(0002) diffraction peak at 2θ = 35.86° corresponds to a lattice constant c film = 5.016 Å for AlN epitaxial film. From the measured lattice constant, the internal stress along c -axis of AlN films is determined to be 1.9 GPa, indicating that the film exhibited a very low tensile stress along the c -axis and a small compressive stress in the a – b plane.…”

Ferroelectric Aluminum Scandium Nitride Thin Film Bulk Acoustic Resonators with Polarization‐Dependent Operating States

“…It has been shown that the thin-film stress can significantly affect the piezoelectric coefficients and k t 2 . [19,28] Yokoyama et al showed that the piezoelectric coefficient of the AlN-based FBAR would decrease by increasing the external stress, acting as a tuning knob to modulate the piezoelectric coefficient. The k 2 of the FBAR is also estimated by Yokoyama et al, using the first-principle calculation, which demonstrated a similar trend as the piezoelectric coefficient.…”