Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0 0 0 1) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

[1]  John E. Ayers,et al.  The measurement of threading dislocation densities in semiconductor crystals by X-ray diffraction , 1994 .

[2]  James S. Speck,et al.  Role of threading dislocation structure on the x‐ray diffraction peak widths in epitaxial GaN films , 1996 .

[3]  Oliver Ambacher,et al.  Thermal stability and desorption of Group III nitrides prepared by metal organic chemical vapor deposition , 1996 .

[4]  R. Felice,et al.  Energetics of AlN thin films on the Al2O3(0001) surface , 1998 .

[5]  Ke Xu,et al.  Polarity inversion of GaN films by trimethyl–aluminum preflow in low-pressure metalorganic vapor phase epitaxy growth , 2002 .

[6]  M. Shur,et al.  Near-band-edge photoluminescence of wurtzite-type AlN , 2002 .

[7]  M. Asif Khan,et al.  AlN/AlGaN superlattices as dislocation filter for low-threading-dislocation thick AlGaN layers on sapphire , 2002 .

[8]  G. Bruno,et al.  Role of sapphire nitridation temperature on GaN growth by plasma assisted molecular beam epitaxy: Part II. Interplay between chemistry and structure of layers , 2002 .

[9]  J. Jasinski,et al.  Inversion domains in AlN grown on (0001) sapphire , 2003 .

[10]  T. Kuech,et al.  X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism , 2003 .

[11]  Yiying Wu,et al.  Effect of nitridation on polarity, microstructure, and morphology of AlN films , 2004 .

[12]  J. Jasinski,et al.  Effect of initial process conditions on the structural properties of AlN films , 2004 .

[13]  Hui Yang,et al.  Surface morphology of AlN buffer layer and its effect on GaN growth by metalorganic chemical vapor deposition , 2004 .

[14]  K. Kawaguchi,et al.  Defect Structures of AlN on Sapphire (0001) Grown by Metalorganic Vapor-Phase Epitaxy with Different Preflow Sources , 2005 .

[15]  Toru Kinoshita,et al.  Polarity dependence of AlN {0001} decomposition in flowing H2 , 2007 .

[16]  David W. Weyburne,et al.  Correlation between optoelectronic and structural properties and epilayer thickness of AlN , 2007 .

[17]  S. Kamiyama,et al.  Annihilation mechanism of threading dislocations in AlN grown by growth form modification method using V/III ratio , 2007 .

[18]  Toru Kinoshita,et al.  Al- and N-polar AlN layers grown on c-plane sapphire substrates by modified flow-modulation MOCVD , 2007 .

[19]  Jia Haiqiang,et al.  Three-Step Growth Optimization of AlN Epilayers by MOCVD , 2008 .

[20]  Michael Heuken,et al.  Effect of the AIN nucleation layer growth on AlN material quality , 2008 .

[21]  Toru Nagashima,et al.  Investigation of void formation beneath thin AlN layers by decomposition of sapphire substrates for self-separation of thick AlN layers grown by HVPE , 2010 .

[22]  U. Mishra,et al.  Polarity inversion of N-face GaN using an aluminum oxide interlayer , 2010 .

[23]  M. Kneissl,et al.  Investigation of inversion domain formation in AlN grown on sapphire by MOVPE , 2012 .

[24]  K. Hiramatsu,et al.  Microstructure of AlN Grown on a Nucleation Layer on a Sapphire Substrate , 2012 .

[25]  P. Parbrook,et al.  AlN heteroepitaxy on sapphire by metalorganic vapour phase epitaxy using low temperature nucleation layers , 2013 .

[26]  J. Ha,et al.  Effect of Al pre-deposition on AlN buffer layer and GaN film grown on Si (111) substrate by MOCVD , 2013, Electronic Materials Letters.

[27]  Ji Shi,et al.  Controlled polarity of sputter-deposited aluminum nitride on metals observed by aberration corrected scanning transmission electron microscopy , 2013 .

[28]  Zhang Zhiwei,et al.  In situ observation of two-step growth of AlN on sapphire using high-temperature metal–organic chemical vapour deposition , 2013 .

[29]  Zhang Zhiwei,et al.  Influence of the growth temperature of AlN nucleation layer on AlN template grown by high-temperature MOCVD , 2014 .

[30]  Brian B. Haidet,et al.  Sapphire decomposition and inversion domains in N-polar aluminum nitride , 2014 .

[31]  Jun Luo,et al.  Mechanism of TMAl pre-seeding in AlN epitaxy on Si (111) substrate , 2014 .

[32]  R. Boichot,et al.  Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy , 2014 .

[33]  S. Chua,et al.  Influences of group-III source preflow on the polarity, optical, and structural properties of GaN grown on nitridated sapphire substrates by metal-organic chemical vapor deposition , 2015 .

[34]  O. Nam,et al.  Fabrication of AIN Nano-Structures Using Polarity Control by High Temperature Metalorganic Chemical Vapor Deposition. , 2015, Journal of nanoscience and nanotechnology.

[35]  L. D. Negro,et al.  Deep-UV optical gain in AlGaN-based graded-index separate confinement heterostructure , 2015 .

[36]  Yong O. Wei,et al.  Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition , 2015 .

[37]  Yong O. Wei,et al.  Growth of high‐quality AlN layers on sapphire substrates at relatively low temperatures by metalorganic chemical vapor deposition , 2015 .

[38]  Z. J. Yang,et al.  High-resistance GaN epilayers with low dislocation density via growth mode modification , 2016 .

[39]  Daishi Inoue,et al.  Performance Improvement of AlN Crystal Quality Grown on Patterned Si(111) Substrate for Deep UV-LED Applications , 2016, Scientific Reports.

[40]  R. Felice,et al.  Polarity Control in Group-III Nitrides beyond Pragmatism , 2016 .

[41]  L. D. Negro,et al.  Deep-Ultraviolet Emitting AlGaN Multiple Quantum Well Graded-Index Separate-Confinement Heterostructures Grown by MBE on SiC Substrates , 2017, IEEE Photonics Journal.

[42]  Young Jae Park,et al.  Influence of TMAl preflow on AlN epitaxy on sapphire , 2017 .

[43]  Haiding Sun,et al.  Droop-free AlxGa1-xN/AlyGa1-yN quantum-disks-in-nanowires ultraviolet LED emitting at 337 nm on metal/silicon substrates. , 2017, Optics express.

[44]  B. S. Ooi,et al.  Self-planarized quantum-disks-in-nanowires ultraviolet-B emitters utilizing pendeo-epitaxy. , 2017, Nanoscale.