Growth of Non-Polar a-Plane AlGaN Epilayer with High Crystalline Quality and Smooth Surface Morphology

Authors: Abbas Nasir, Xiong Zhang, Sohail Ahmad, Yiping Cui

Abstract:

Non-polar a-plane AlGaN epilayers of high structural quality have been grown on r-sapphire substrate by using metalorganic chemical vapor deposition (MOCVD). A graded non-polar AlGaN buffer layer with variable aluminium concentration was used to improve the structural quality of the non-polar a-plane AlGaN epilayer. The characterisations were carried out by high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM) and Hall effect measurement. The XRD and AFM results demonstrate that the Al-composition-graded non-polar AlGaN buffer layer significantly improved the crystalline quality and the surface morphology of the top layer. A low root mean square roughness 1.52 nm is obtained from AFM, and relatively low background carrier concentration down to 3.9×  cm^-3 is obtained from Hall effect measurement.

Keywords: Non-polar AlGaN epilayer, Al composition-graded AlGaN layer, root mean square, background carrier concentration.

References:

[1] Cho, C.-Y., et al., Enhanced emission efficiency of GaN-based flip-chip light-emitting diodes by surface plasmons in silver disks. Applied Physics Express, 2012. 5(12): p. 122103.
[2] Shur, M.S. and R. Gaska, Deep-ultraviolet light-emitting diodes. IEEE Transactions on electron devices, 2009. 57(1): p. 12-25.
[3] Würtele, M., et al., Application of GaN-based ultraviolet-C light emitting diodes–UV LEDs–for water disinfection. Water research, 2011. 45(3): p. 1481-1489.
[4] Chen, R.Z., S.A. Craik, and J.R. Bolton, Comparison of the action spectra and relative DNA absorbance spectra of microorganisms: Information important for the determination of germicidal fluence (UV dose) in an ultraviolet disinfection of water. Water research, 2009. 43(20): p. 5087-5096.
[5] Meduri, N.B., et al., Phototherapy in the management of atopic dermatitis: a systematic review. Photodermatology, photoimmunology & photomedicine, 2007. 23(4): p. 106-112.
[6] He, J., et al., Study of NH3 flow duty-ratio in pulsed-flow epitaxial growth of non-polar a-plane Al0. 34Ga0. 66N films. Materials Science in Semiconductor Processing, 2019. 90: p. 219-224.
[7] Laskar, MR, et al., High-resolution X-ray diffraction investigations of the microstructure of MOVPE grown a-plane AlGaN epilayers. Journal of Crystal Growth, 2011. 315(1): p. 208-210.
[8] Jo, M., et al., Structural and electrical properties of semipolar (11‐22) AlGaN grown on m‐plane (1‐100) sapphire substrates. physica status solidi c, 2017. 14(8): p. 1600248.
[9] Waltereit, P., et al., Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes. Nature, 2000. 406(6798): p. 865-868.
[10] Nasir, A., et al., Effects of indium surfactant and MgN intermediate layers on surface morphology and crystalline quality of non-polar a-plane AlGaN epi-layers. Optik, 2019: p. 162978.
[11] Fan, A., et al., Enhanced hole concentration and improved surface morphology for non-polar a-plane p-type AlGaN/GaN superlattices grown with indium-surfactant. Superlattices and Microstructures, 2019. 130: p. 396-400.
[12] Wu, Z., et al., Enhanced structural and electrical properties of non-polar a-plane p-type AlGaN/GaN superlattices. Superlattices and Microstructures, 2019. 125: p. 310-314.
[13] Yang, H., et al., γ-Aminobutyric acid ameliorates fluoride-induced hypothyroidism in male Kunming mice. Life sciences, 2016. 146: p. 1-7.
[14] Dai, Q., et al., Effects of Mg-doping on characteristics of semipolar (112¯ 2) plane p-AlGaN films. Materials Letters, 2017. 209: p. 472-475.
[15] Laskar, MR, et al., Distorted wurtzite unit cells: Determination of lattice parameters of non-polar a-plane AlGaN and estimation of solid phase Al content. Journal of Applied Physics, 2011. 109(1): p. 013107.
[16] Yu, HB, et al., Advantages of AIGaN-based deep-ultraviolet light-emitting diodes with an Al-composition graded quantum barrier. Optics Express, 2019. 27(20): p. A1544-A1553.
[17] Hiroki, M. and K. Kumakura, Ohmic contact to AlN:Si using graded AlGaN contact layer. Applied Physics Letters, 2019. 115(19): p. 4.
[18] Zhao, J., et al., Defects reduction in a-plane AlGaN epi-layers grown on r-plane sapphire substrates by metal organic chemical vapor deposition. Applied Physics Express, 2016. 10(1): p. 011002.
[19] Tao, P., et al., Crack-free Al0. 5Ga0. 5N epilayer grown on SiC substrate by in situ SiNx interlayer. Materials Science in Semiconductor Processing, 2016. 41: p. 291-296.
[20] Tang, K., et al., The roles of buffer layer thickness on the properties of the ZnO epitaxial films. Applied Surface Science, 2016. 388: p. 557-564.
[21] Van de Walle, C.G., DX-center formation in wurtzite and zinc-blende Al x Ga 1− x N. Physical Review B, 1998. 57(4): p. R2033.
[22] Zhang, G., et al., Relationship of background carrier concentration and defects in GaN grown by metalorganic vapor phase epitaxy. Applied physics letters, 1997. 71(23): p. 3376-3378.