The control of primary nucleation during the vapour-phase growth of single crystals can be accomplished by means of periodical temperature oscillations in either source or growth zone or in both, so as to have periodical super- and undersaturation (i.e., growth and etching) conditions in the growth ambient. In this way, the secondary nucleation of the first formed nuclei is statistically favoured at the expense of subsequent primary nucleations. In this communication, an electronic set-up suitable for programming these oscillating temperature profiles is described. In particular, the simplicity and versatility of the electronic circuit is underlined, where the comparison of the ramp levels is made digitally and not, as commonly reported, by means of analogic comparators with a remarkable increasing of the accuracy in the profile control. © 1979.
