Modeling and simulation are used for the design of electrically pumped semiconductor based light emitters and for investigation of their physical properties. Examples of such devices are quantum-dot based single-photon sources and vertical cavity surface emitting lasers. This is a part of a cooperative project between WIAS and ZIB within the DFG Collaborative Research Center 787 (SFB 787), "Semiconductor Nanophotonics: Materials, Models, Devices". The research center combines three complementary areas of research aiming at the development of novel photonic and nanophotonic devices. The close collaboration between the different research areas and their mutual integration will help to explore new functionalities of nanophotonic devices and will open new dimensions of applications. These include quantum key systems that are based on single photon and entangled photon emitters, high frequency vertical cavity surface emitting lasers, and quantum dot lasers.