kobayashi-mrssp-468-187

Data for reference kobayashi-mrssp-468-187

Initial Stages of MOCVD Growth of Gallium Nitride Using a Multistep Growth Approach

J.T. Kobayashi, N.P. Kobayashi, P.D. Dapkus, X. Zhang, D.H. Rich

Materials Research Society Symposium Proceedings 468, 187 (1997).

Below is the abstract submitted to the meeting, not the abstract of the published paper:
The growth of GaN on (0001) sapphire substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) equipped with a close spaced showerhead reactor is studied. Three distinct macroscopic evolution stages are observed and identified as follows: (l) the first stage, where truncated 3D islands (TTIs) are grown on low-temperature grown buffer layers, (2) the second stage, where TTIs are merged laterally to form continuous film, and (3) the third stage, where 2D growth takes place. A multistep growth sequence in which growth conditions for each layer are optimized to obtain TTIs of uniform height and make the islands cover the entire buffer layer is introduced. A multilayer buffer layer strategy has been developed in which the thermal desorption and mass transport of the low temperature buffer layer are minimized by deposition of successive layers at increasing temperatures. The temperature for the overlayer growth is a tradeoff between the need to inhibit thermal desorption and mass transport of the buffer layers and the need to increase surface mobility to increase the lateral growth rate of the TTIs relative to their vertical growth rate. Therefore, also for overlayer growth, multistep growth sequence is used. Using this approach, we have been able to reduce the temperature of the growth to achieve smooth morphology and excellent characteristics. This paper will report the comparisons of the growth conditions of each layer, the morphology of TTIs and the electrical, structural and optical properties of the final overlayer. By using multistep growth and optimizing the growth conditions for each layer to form TTIs which have uniform height and cover the entire buffer layer, high quality GaN with featureless surface morphology is obtained. Double crystal x-ray diffraction rocking curves for GaN (0002) show FWHM values of ∼240 arc sec.

This paper is part of Gallium Nitride and Related Materials II

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