Technology and Characterization of Single-Crystalline Substrates Made of ZnSe-Based Wide-Gap II-VI Semiconductor Compounds

Abstract

Detrimental role of traces of oxygen in the growth process of the ZnSe-based wide-gap II-VI semiconductor crystals is emphasized. Adhesion, enhanced by the presence of oxygen, of the growing crystal to the walls of the quartz ampoule promotes generation of twinning and dislocations. The technology of the substrate-quality crystals, which ensures nearly complete removal of oxygen, is described. The results of characterization of the obtained large (25 mm diameter), twin-free single crystals of ZnSe, and substrate plates are presented.Introduction The II-VI semiconductor technology based on epitaxy (MBE, MOCVD) requires substrates, which have to be cut out of very high quality single crystals (at least 1 inch diameter), preferentially of the II-VI compound, as generally much better results can be achieved with homoepitaxy rather than with heteroepitaxy. It has been shown for example [1], that creation of a very bad interface accompanies the heteroepitaxial growth of ZnSe on a GaAs substrate. To avoid twinning, which plagues hightemperature crystallization, the methods of growth at temperatures lower than the melting point, like solid-phase recrystallization [2], chemical vapour transport and physical vapour transport (PVT) [3], are widely investigated and developed.We are using self-seeded PVT for the growth of ZnSe and Zn(Se,S) substrate crystals (1 inch diameter). Our high-quality crystals have been described e.g. in [4]. The poor reproducibility of the successful growth was the biggest remaining problem, and the growth of crystals with larger diameters appeared to be impossible. Now, the main reasons of the difficulties seem to be found. Beside not always perfect stoichiometry, it is residual oxygen.

Chemical Etching and TEM Crystalline Quality Assessment of Single Crystalline ZnSe Ingots Grown by I2 Vapor Phase Transport

“…The elements used in ZnSe growth were commercially obtained (Alpha Aesar-Puratronic) with purity of 6N in the case of Zn and 5N in the case of Se. Both elements were separately distilled at least three times in dynamic vacuum to reduce impurities and to avoid the oxidized elements presence [8][9][10][11][12][13][14] (Figure 1). Torr).…”

“…Occluded crystals lack ensures greater useful volume available for devices manufacture. Also some twins (Figure 4b) could be observed in a different wafer showing that oxygen removal was not properly done [11] meanwhile ampoule charge. When growth conditions were accomplished then ZnSe single crystalline ingots were evenly yellowish and transparent (Figure 2) though ingot (F) presented in this paper had the best mentioned properties.…”