Rheed signal sampling device

Abstract

Monitoring the intensity of the reflected spot in a RHEED image is the most important method used to control the growth of semiconductor crystals in facilities like for example MBE. In some application the availability of the spot intensity signal as an analog voltage is also useful to realize a feedback between the growth dynamics and the external parameters of the plant, such as the cells temperatures and the syn-chronization of the shutters. Although said analog signal could be obtained by using a photo-detector near the RHEED screen or grabbing and digitizing the RHEED image, these methods are troublesome or expensive respectively. In this paper a simple and cheap solution, based on a synchronized sample and hold operation on the composite video signal, is proposed.