Growth of high‐quality AlN at high growth rate by high‐temperature MOVPE

Abstract

AlN layers were grown by high-temperature MOVPE. A systematic analysis of high-temperature growth of AlN was carried out and the resultant layers were analyzed by X-ray diffraction and atomic force microscopy. The structural quality and the morphology of AlN layers improve with rising growth temperature.1 Introduction Dramatic improvement of the crystalline quality of GaN grown on a sapphire substrate by the low-temperature buffer layer technique [1] and control of the conductivity of the nitrides [2][3][4] have led to the evolution of high-efficiency optoelectronic devices in the visible short-wavelength region. Group III nitride semiconductors are promising potential for optoelectronic applications, particularly in the UV region. In order to realize UV-optoelectronics applications, it is necessary to grow highcrystalline-quality AlN.The main emphasis in this study is to grow better quality AlN layers by metalorganic vapor phase epitaxy (MOVPE). Among the prominent nitride semiconductors such as, GaN, AlN, InN and their alloys, with the notable exception of AlN and its alloys, layers of high-quality most of the materials can be grown at temperatures of 1200 °C or less. The crystalline quality of AlN layers is always inferior to its counterpart GaN grown at much lower temperatures. The high temperature growth of AlN films is expected to be effective in improving crystalline quality and surface morphology because surface migration of Al-species would increase at high temperatures. There are few reports on AlN growth at high temperatures on the order of 1350 °C [5,6] due probably to the instrumental limitation.In this study, we made an attempt to systematically study the high-temperature growth of AlN on (0001) sapphire substrates. The temperatures are in the range from 1200 to 1500 °C. In addition, the influence of the V/III ratio on the growth rate of AlN was observed by performing growth at three different values of the V/III ratio.

Growth of high-quality and crack free AlN layers on sapphire substrate by multi-growth mode modification

“…This is due to the island growth in the case of multi-growth mode modification. It is reported that the growth rates of AlN decrease with increasing V/III ratio when HT-MOVPE is used [4]. On the basis of this report, it is thought that the growth mode is changed by changing the V/III ratio before it transfers from island growth to two-dimensional growth, although the mechanism is not yet clear.…”

“…For these reasons, we focus on the high-temperature (HT) MOVPE growth of AlN. Furthermore, an atomically flat surface can be obtained when AlN growth is performed at temperatures higher than 1300 1C [4]. However, the X-ray diffraction rocking curve full-width at half-maximum (FWHM) of asymmetric planes was wider than 1,000 arcsec, which means that the HT-grown AlN contains high-density dislocations.…”

“…However, a LT buffer layer is less effective in the case of AlN growth. On the other hand, high-quality AlN layers have been obtained using higher growth temperatures and low V/III ratios by MOVPE [3,4]. For these reasons, we focus on the high-temperature (HT) MOVPE growth of AlN.…”

Epitaxial lateral overgrowth of a-AlN layer on patterned a-AlN template by HT-MOVPE

“…One of the methods to improve the crystalline quality is epitaxial lateral overgrowth (ELO) [5][6][7][8]. Furthermore, in relation to AlN growth on c-plane sapphire, the crystalline quality of AlN by high-temperature metal-organic vapor phase epitaxy (HT-MOVPE) is much improved than that grown at conventional temperatures [9,10].…”

Chemical Reaction Pathways for MOVPE Growth of Aluminum Nitride

“…The residence time of the gas was set to 1 s, the pressure was set to 100 Torr, and the V/III ratio was set to 115. These values were determined by referencing previous reports by Amano 10,11 describing AlN growth with reduced parasitic reactions. The gas temperature was set to 300…”