........ published in NEWSLETTER # 59
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........ published in NEWSLETTER # 59
HETEROSTRUCTURE EPITAXY AND DEVICES
by Dr. J. Novak, Slovak Academy of Sciences (Slovakia) and Professor A. Schlachetzki, Technical University, Braunschweig (Germany)
In October 1995, an international workshop on "Heterostructure Epitaxy and Devices" was held at Smolenice Castle some 60 km north of Slovakia's Capital Bratislava. The contributions emerging from the workshop and compiled in this volume (NATO ASI SERIES 3-11) can be grouped into five sections. Fundamental to all groups is the epitaxial growth where metalorganic vapour-phase epitaxy (MOVPE) is dominating, with a number of contributions on molecular-beam epitaxy (MBE) and on liquid-phase epitaxy. Both MOVPE and MBE are covered by realtime monitoring and simulation of growth. The second group centres on heterostructures which can be characterized by scanning tunnelling microscopy down to atomic resolution.
In the third group of contributions, composite systems were discussed, i.e. epitaxial films and substrates differing in lattice constant, thermal expansion coefficient, or crystal structure. At present the most conspicuous example is column-III nitrides grown on sapphire, developed for LEDs and lasers emitting in the blue and violet range of the spectrum. In many respects similar phenomena are observed with III/V compound semiconductors on silicon substrates.
Several techniques are available to assess the quality of
epitaxial layers. Among them is atomic force microscopy to study the fundamental growth mechanisms, high precision x-ray diffractometry particularly for heterostructures or lift-off of layers. All epitaxial growth is done with device application in mind. Thus the final group of contributions concentrates on devices. A wealth of devices of outstanding performance can be grown by MOVPE. Among them are heterostructure bipolar transistors, high-electron-mobility transistors, and tunnelling heterostructure devices.
Reference books: 3-11, B180, B340, E87, E243, E270, E286, E298