In situ structuring during MBE regrowth with shadow masks

We discuss the possibilities of MBE regrowth through shadow masks for semiconductor technology. II–VI and III–V compound semiconductors have been deposited into fixed shadow masks developed from AlGaAs/GaAs layers on GaAs [0 0 1] substrates. Adjusting the directions of the molecular beams relative to the masks enables in situ lateral structuring by layer offset. As another growth mode we utilize an effect based on zero sticking of atoms that cannot reach their compound partner. Thus, growth is mainly restricted to the overlap of the molecular beams. In small mask dimensions the partial shadows shrink and self-assembling effects play a major role. Smooth [1 1 1] facets are observed in most cases, but dependent on material and mask orientation [1 1 4], vertical [1 1 0] or even not any facets form. ZnSe-based compound semiconductors are well suited for nanostructuring (sub- 100 nm resolution) as diffusion lengths along [1 −1 0] reveal to be very small. Therefore stripes oriented in [1 1 0] direction show steep edges, which may serve for secondary shadowing the molecular beams. We demonstrate this technique with a complex sample structures. Its basic idea is to use shadow growth for the realization of selective contacts on nominally overgrown layers. Two different in situ contacts have been deposited in order to selectively contact individual parts of the structure.