Large-area high-quality single crystal diamond
- PDF / 659,414 Bytes
- 7 Pages / 585 x 783 pts Page_size
- 95 Downloads / 221 Views
Introduction The high-pressure high-temperature (HPHT) technique that mimics the natural formation process of diamond deep inside the earth and chemical vapor deposition (CVD) that works far from thermodynamic equilibrium below ambient pressure are synthesis routes that were discovered nearly contemporaneously in the first half of the 1950s. While the former quickly reached the level of an industrial production method, CVD of diamond was not considered a serious alternative until technologically relevant growth rates in the micron-per-hour range were shown by Japanese scientists in the 1980s (see the Introductory article in this issue and Reference 1). A large number of different methods for the activation of the gas phase in the CVD process were subsequently developed. They facilitated an easy overcoming of the inherent size limitations of the HPHT technique (∼1 cm) and provided a variety of polycrystalline diamond layers differing in grain size, texture, impurity content, resistivity, and transparency. Polycrystalline diamond has been established in various demanding applications (heat spreaders, infrared and microwave windows, and wear resistant coatings). In several applications, however, the polycrystalline nature prevents diamond devices from achieving the ultimate performance levels expected from single crystal diamond (SCD) parameters. As a consequence,
electronic devices suffer from drastically reduced charge carrier mobility2 and detectors from incomplete charge collection.3 The fundamental feasibility of high-quality SCD synthesized by CVD has already been demonstrated convincingly. In homoepitaxial samples of diamond grown on HPHT crystals, mobility values of holes and electrons are close to the theoretical limit,4,5 and a charge collection efficiency approaching unity can be achieved.6 In order to profit from these outstanding results, technology for the reproducible manufacturing of SCD with appropriate size and structural quality is required. This article describes the different approaches that are currently being undertaken to reach this goal. In the first part of this article, the issue of high rate homoepitaxial growth is addressed. Basically, several different activation methods have the potential for deposition rates of several 10 µm/h.7 Here, we focus on microwave plasmaassisted chemical vapor deposition (MPACVD) as the most prominent method that combines excellent film purity with high growth rates that are homogeneous over acceptable areas. Furthermore, tiling as a powerful concept to increase the lateral size is described. Heteroepitaxy provides a completely different approach to synthesize SCD on scalable substrates. In the second part of the article, after a brief survey of explored substrate materials, we concentrate on
Matthias Schreck, Institute of Physics, University of Augsburg, Germany; [email protected] Jes Asmussen, Michigan State University, USA; [email protected] Shinichi Shikata, National Institute of Advanced Industrial Science and Technology, Japan; s-shik
Data Loading...
