For the last two decades, group III nitrides have attracted much attention because of their excellent optical and electrical properties. These materials have been successfully utilized for fabrication of efficient blue LEDs, lasers, and FETs. So far, growth of thin film III nitrides has been performed by MOCVD or MBE at high temperatures, above 700°C. This high growth temperature limits the growth substrates to thermally stable materials such as sapphire. However, sapphire has large mismatch in both lattice constants and thermal expansion coefficients with the group III nitrides and it is well known that these both mismatch types cause degradation in crystalline quality. We have recently found that the use of pulsed laser deposition (PLD) allows us to improve surface migration of the film precursors and to reduce the growth temperature down to room temperature (RT). [1-9] Hence, we can expect that the use of PLD makes it possible to use various chemically vulnerable substrates with small mismatches such as ZnO and Hf. In this presentation, we will discuss advantages of RT epitaxial growth of group III nitrides on the substrates with small mismatches by PLD.

Growth of group III nitrides was performed using an rf-plasma-assisted UHV-PLD apparatus. Various materials which include ZnO, MnZn ferrite, LiGaO₂, and Hf, were used as substrates for RT growth. Group III metals such as In, Al, and Ga were irradiated with a KrF excimer laser light at an energy density of about 3.0 J/cm² and reacted with active nitrogen generated by rf-plasma. After the film growth, we characterized the structural properties of the RT grown nitride films by EBSD, RHEED, HRXRD, AFM, photoluminescence, and GIXR.

We have observed clear streaky RHEED patterns and their intensity oscillation during the RT growth, which indicates that the RT growth proceeds epitaxially in the layer-by-layer mode. HRXRD measurements have revealed that reduction in growth temperature leads to improvement in crystalline quality of nitrides probably due to the suppression in the interfacial reactions between the nitrides and the substrates. This improvement of crystalline quality is particularly important when it is used for the growth of non-polar nitrides because the film quality of nonpolar nitrides achieved by conventional high temperature growth techniques is quite poor. We have also found that the reduction in growth temperature suppresses the phase separation of InGaN. The InGaN films grown at RT exhibited a sharp X-ray peak with single component and a strong photoluminescence at long wavelengths. We have found that reduction in growth temperature also suppresses the introduction of misfit dislocations at the heterointerfaces between the nitrides and the substrates. These results indicate that the RT growth technique is quite promising for fabrication of nitride optical and electron devices with high performance.

References

[1] K. Ueno, A. Kobayashi, J. Ohta, and H. Fujioka, Appl. Phys. Lett., (in press).

[2] A. Kobayashi, S. Kawano, Y. Kawaguchi, J. Ohta, and H. Fujioka, Appl. Phys. Lett., 90, 041908 (2007).

[3] G. Li, T.- W. Kim, S. Inoue, K. Okamoto, and H. Fujioka, Appl. Phys. Lett., 89, 241905 (2006).

[4] T.-W. Kim, N. Matsuki, J. Ohta, and H. Fujioka, Appl. Phys. Lett., 88, 121916 (2006).

[5] A. Kobayashi, J. Ohta, H. Fujioka, K. Fujiwara, and A. Ishii, Appl. Phys. Lett., 88, 181907 (2006).

[6] S. Inoue, K. Okamoto, N.Matsuki, T. W. Kim, and H. Fujioka, Appl. Phys. Lett., 88, 261910 (2006).

[7] M.-H. Kim, M. Oshima, H. Kinoshita, Y. Shirakura, K. Miyayama, J. Ohta, A. Kobayashi, and H. Fujioka, Appl. Phys. Lett., 89, 031916 (2006).

[8] A. Kobayashi, Y. Kawaguchi, J. Ohta, and H. Fujioka, Appl. Phys. Lett., 89, 111918 (2006).

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/10584 must be provided.

1. Epitaxial growth of semipolar Al_xGa_1-xN(1-103) films on ZnO substrates using room temperature buffer layer