The characterizations of superlattices and delta-doped epi-layers grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) have been investigated. As an basic study, the electrical properties of n-$Al_xGa_{1-x}AS$ ($00.2$) due to deep DX center have been investigated. The anomalous conduction band density of states which can be found in the course of the anayses of the Hall-effect measurement results, has been confirmed. Moreover, the physical origin for this anomaly was also discussed. On the basis of this basic study, the growth technology of GaAs/AlGaAs superlattices and modulation doped heterostroctures has been studied. By the proper undestandings of flow patern during growth and design parameters of a reactor, it was proven using photoluminescence, double crystal x-ray diffraction, Hall-effect, C-V profiling and quantum-Hall effect measurements, that the successful growth of these novel structures was possible by MOCVD. The growth technology has been extended to the study of delta-doping which is arised as a novel doping technique and is mainly done by MBE. Although the growth temperatures for delta-doped layer by MOCVD is as higher as $150\,^\circ\!C$ than those of MBE, it was found utlizing C-V profiling, Hall-effect and Shubnikov de Haas (SdH) measurements, that the excellent delta-doping profiles were resulted. This excellent result implies and additional diffusion limiting mechanism which is absent in MBE growth. One possible model for this mechanism is suggested. In addition, a perliminary delta-FET has been fabricated to see the feasibliity of the application. The GaAs-on-Si technology which has been drawn much attentions due to its commercial utility has been studied. To reduce the dislocation density, i...