as shown by fig1 and 3 uses an arrangement where the substrate 58 which is shown in the shutter position may be physically moved over the selected sources 68 and 70 or other sources not shown when these separate sources which contain different alloy compositions are exposed to substrate 58 during selected periods of time during the process these sources will provide different epitaxial growths having differing electro optic characteristics for example the substrate 58 can be in the shuttered position until the furnace chamber is heated up to a desired growth temperature and then the substrate 58 positioned over source 68 for the first layer growth and over source 70 for the second layer growth then back to the shuttered position for cool down multi source arrangements may also be provided with the added technique as mentioned above with respect to the single source wherein different reactive gases may be used during the process to provide even better variations of the electrical and optical properties of the layers it should be noted that the above explained method of producing epitaxially grown layers on semiconductor substrated under reactive gas pressures employing loading the growth elements in a reusable demountable ampule having vent means to provide semiconfinement of the epitaxial process provides control of a more desirable x value profile in the epitaxial layer thickness the present pressurized process allows for epitaxial growths at a lower temperature than was previously possible one example of how an epitaxially grown 20 micron thick hg 0 8 cd 0.