Extension of the epitaxial shadow mask MBE technique for the monolithic integration and in situ fabrication of novel device structures

We present new methods for the in situ fabrication of novel device structur es based on the epitaxial shadow mask (ESM) MBE technique. For high-quality selective contacts, the deposition of the dopants must exactly be aligned to the angular position of the substrate during growth. With a specially de signed real-time software, we can either use the delta-doping (rotation and growth stopped while doping at a certain angular position) or the flash-do ping technique (continuous rotation and growth with dopant shutters open in a certain angular window only). As an extension for devices where more tha n two selective contacts are required, an enhanced version of the shadow ma sk, a 2D-patterned one, is presented. In order to monolithically integrate a n-i-p-i modulator with a photoconductive switch and a reference diode, we also introduce a new technique using a special kind of shadow mask. Select ive etch processes allow to integrate functional epi-layers into a "smart" shadow mask and to fabricate monolithically integrated smart pixels (MISPs) , which are suitable for 2D arrays. (C) 1999 Elsevier Science B.V. All righ ts reserved.