PACS 72.80. Ey, 78.55.Cr One of the most important questions in the application of the close spaced vapour transport method of epitaxial growth of various compound semiconductors is the appropriate doping of the growing layer. In this work low temperature photoluminescence spectra were taken on GaAs epitaxial layers grown by water-inhydrogen transport method using n, p, and i (semi-insulating) type conductivity source crystals. Two different water vapour pressures were applied for the experiments. The transport and incorporation of impurities from the source were clearly indicated in combination with some specific, probably defect and/or complex related photoluminescence peaks.Introduction According to some proverbs, cats have three (sometimes nine) lives. Perhaps one can make similar conclusions, when studying the history of semiconductors and technologies of semiconductors. E.g. we have indicated in [1] that this era is the third "life" of GaN. There is a similar situation now for a technological method, for the close space vapour transport (CSVT). The method was proposed (and investigated) in early and mid-sixties [2 -4]. (Though according to words of [5] "such a technique always existed".) This was the "great" starting period of vapour phase technologies. The second era for CSVT was the second half of the eighties, and the beginning of the nineties [6,7].By that time the vapour phase epitaxy techniques based on halogen transport became widespread and the method based on metal-organic precursors was developed for binary and ternary III-V compounds. Nevertheless CSVT still remained an attractive technology. Simplicity, inexpensive setup, absence of toxic gases (and expensive safety systems), high growth rates, etc. characterise this method. The possibility to grow semi-insulating (SI) or nearly SI GaAs with controlled EL2 concentration gave a great impact to the use of CSVT [8,9]. Preparation of photovoltaic structures, especially GaAs on Ge heterostructures, was the other dominant direction of CSVT applications [6,10].The second revival, the third era is the present time, when the solar-energy conversion is the main aim. CSVT has been applied to III -Vs, like GaAs on Si, InGaP on GaAs, even combined with LPE method [11,12]. The basic direction is, in II-VIs. Well known materials have been revived in this technology: ZnO, ZnTe, ZnSe, CdTe, CdIn 2 Te 4 , and there is a new approach to the CIS structures of the greatest importance: CuInSe 2 and CuIn 1-x Ga x Se 2 (only examples: [13,14]). CIS is one of the most fashionable research topics in vogue and, the future of cheap, large area solar cells may depend on the cheap, fast, safe CSVT method.
