| SM ISO690:2012|
RAEVSCHI, Simion; BOTNARIUC, Vasile; GORCEAC, Leonid; POTLOG, Tamara; DOBROMIR, Marius; LUCA, Dumitru. Surface composition of GaN, AlGaN LAYERS GROWN ON Si substrates investigated by XPS. In: Materials Science and Condensed Matter Physics. Editia a 8-a, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, p. 281. ISBN 978-9975-9787-1-2.
|Materials Science and Condensed Matter Physics
Editia a 8-a, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016
The gallium nitride layers, the solid solutions based on aluminum nitride or indium used in the manufacturing of optoelectronic devices are usually grown on sapphire substrates or silicon carbide. These substrates are expensive, not available on the necessary size. Therefore the development of technology of fabrication of GaN layers on heterogeneous and cheap substrates, it is one of the current issue in semiconductor technology. Special attention in this aspect, as the substrate, silicon is given. But the growth of epitaxial GaN layers directly on Si is difficult to achieve because of the interaction between Si and nitrogen, synthesizing Si3N4, freeing gallium at the interface layersubstrate, deterioration of heterojonction. In this paper, in order to avoid this phenomenon before synthesizing GaN layer on Si (111) we successively deposited two AlN nano-metric layers and one of AlGaN. Synthesis of the layers was carried out by Hydride Vapor Phase Epitaxy Method (HVPE) in a horizontal quartz reactor installed in a four-zone electrical furnace. As precursors hydrogen, ammonia, hydrogen chloride, aluminum and gallium (5N) were used. Before being introduced into the reactor substrates with 50 mm diameter were degreased in organic solvents, corroded in basic and acidic solutions standard for silicon. During the deposition of layers the substrates were rotated with a hydrogen flow at a rate of 50-100 Hz. The growth of the layers was carried out in several stages. The first layer of AlN-1 was deposited at (1100 ± 10) 0C during 1-2 min. The second layer of AlN-2 deposited at the same duration as AlN-1 and third interlayer AlGaN (10 min) were deposited at the deposition temperature as for GaN (9500C and 10000C). The surface composition of the AlGaN layers (samples 153, 156) and GaN (samples 156; 162; 164) was studied by XPS (X-ray photoelectron spectroscopy). XPS spectra were measured using PHI-500 Versa Probe, ULVAC-PHI/Physical Electronics X-ray photoelectron spectrophotometer with AlK monochromatic radiation (1486.7 eV). Photoelectrons were collected at an angle of 450. Surface composition (in at. %) of elements is present in the table below. Besides nitrogen, aluminum and gallium the GaN layers contain a high procentage of carbon and oxygen. It is assumed that the carbon derived from graphite used in the reactor quartz to protect interaction with synthesized compounds. As has been shown in  oxygen occurs in GaN layers under exposure in atmospheric conditions and can be removed. Also, oxygen can occur from decomposition of SiO2 components at high temperatures. We note that in samples 153, 155, for which AlN layers were grown at 11000C and not covered with a GaN layer deposited at lower temperatures, the oxygen concentration is ~2.5 higher as in other samples. In the AlGaN layers the gallium concentration is not greater than 2 at. % in spite of the fact, that the concentration of aluminum and gallium precursors were in the synthesis zone in equimolar ratio.