| 摘要 |
1,194,017. Semi-conductor devices. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 27 Oct., 1967 [1 Nov., 1966], No. 48956/67. Heading H1K. Semi-conductor material is epitaxially deposited on a single crystal substrate from the liquid phase by withdrawing solvent from a molten solution of the semi-conductor material. The solvent may be withdrawn by evaporation or by chemical reaction. In a first example a 20% solution of SiC in chromium is placed on an N-type SiC wafer doped with nitrogen. The assembly is arranged on a pyrographite plate and heated by means of an H.F. coil in a helium atmosphere at reduced pressure to melt the solution from which the chromium evaporates to epitaxially deposit a layer of SiC which is of P-type conductivity due to a small chromium content. The solution may also contain aluminium as an acceptor impurity. In a second example a pattern of disc-shaped pieces of foil of Cr 20% SiC 20% Al are placed on a wafer of nitrogen-doped SiC and covered by a second wafer. On heating, areas of P-typ SiC are simultaneously epitaxially deposited on both wafers to form NPN structures. In a modification a pattern of chromium areas is vapour deposited on a wafer of SiC doped with boron and a second similar wafer is placed on the deposited pattern. The wafers are heated in helium containing 1 % nitrogen and SiC dissolves from the wafers and is regrown as N-type material where the chromium areas were deposited to form PNP structures. In a third example a plate of Ga, 4 mol. per cent GaP, 0À04% Te is placed on a zinc-doped P-type wafer of GaP and heated in an atmosphere of chlorine which reacts with the molten gallium to form volatile gallium chloride, N- type GaP doped with tellurium being epitaxially deposited on the wafer. |
