Influence of substrate temperature on the crystalline quality of AlN layers deposited by RF reactive magnetron sputtering

Abstract

Aluminum nitride (AlN) is a promising material for use in applications such as ultraviolet light-emitting diodes and surface acoustic wave devices. In this study, AlN layers were fabricated on nitrided sapphire substrates using radio-frequency (RF) reactive magnetron sputtering. An AlN layer sputtered in 50 vol% N2 with a sputter power of 900 W at 823 K exhibited X-ray rocking curves for AlN (0002) and (10-12) with the best full width at half-maximum of 61 and 864 arcsec, respectively. The c-axis lattice constant of the AlN layers expanded with increasing substrate temperature because of the peening effect and thermal expansion difference between the AlN layer and sapphire substrate. Based on the results obtained here combined with those of our previous studies, a model explaining the roles of sputtering parameters in AlN layer growth using RF reactive sputtering was developed.

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

“…8 These estimated values of the 200 nm-thick AlN sputtered film were lower than mixed and edge dislocation densities (estimated from the TEM images to be 10 9 and 10 10 cm 2 , respectively) in the 200 nm-thick AlN film sputtered with a power of 900 W using 50 vol%N 2 at 823 K on the c-plane nitride sapphire. 17 The 200 nmthick AlN film sputtered at the highest P O 2 had the same order of the estimated edge dislocation density (10 9 cm -2 ) with that of the AlN layer grown by LPE using N 2 gas with a P O 2 of 10 -1 Pa at a N 2 flow rate of 20 sccm and a Ga-40 mol%Al flux for 5 h at 1573 K on the nitrided c-plane sapphire. 18 The Sq values for the 200 and 300 nm-thick AlN films sputtered at the highest P O 2 were 0.92 and 1.20 nm, respectively.…”

Non‐Polar a‐Plane AlN Growth on Nitrided r‐Plane Sapphire by Ga–Al Liquid‐Phase Epitaxy

“…Figure 1(c) shows the definition of the off-cut angle used in this study. AlN and GaN growth on an r-plane sapphire substrate with an off-cut direction toward [0001] has been previously reported [11][12][13][14]27] ; however, AlN growth on an r-plane sapphire substrate with an off-cut direction toward [11][12][13][14][15][16][17][18][19][20] as shown in Figure 1(c), has not been previously reported. The experimental details for thermal nitridation have been described in previous papers.…”

“…Our group has developed several techniques to fabricate AlN layers on sapphire substrates . In particular, we fabricated high‐quality single crystalline c ‐plane AlN thin films by thermal nitridation on c ‐ and a ‐plane sapphire substrates.…”

“…[14] Our group has developed several techniques to fabricate AlN layers on sapphire substrates. [15][16][17][18] In particular, we fabricated high-quality single crystalline c-plane AlN thin films by thermal nitridation [19,20] on cand a-plane sapphire substrates. Moreover, using Ga-Al liquidphase epitaxy we homoepitaxially grew an AlN layer on a single crystalline AlN thin film formed by sapphire nitridation.…”

Effects of Growth Conditions on AlN Layer Grown by Ga-Al Liquid Phase Epitaxy

“…In our group, we had developed a method for fabricating high-quality AlN thin lms by nitriding sapphire under controlled conditions 18,19) . Using the nitrided sapphire substrate as a template, DC-pulsed sputter deposition 20,21) and RF reactive sputtering techniques 22,23) have been investigated. Recently, authors have developed the Ga-Al liquid phase epitaxy (LPE) technique on the nitrided sapphire substrate, and have successfully grown 1.2-μm-thick AlN layer at 1573 K under normal pressure of N 2 gas for 5 h 24,25) .…”