In the framework of this thesis Ballistic Electron Emission Microscopy/ Spectroscopy (BEEM/S) was used to investigate semiconductor heterostructures. Including organic semiconductors like titanylphthalocyanine (TiOPc) and hexa-peri hexabenzocoronene (HBe. Analyzing the BEEM spectra we find that the TiOPc increases the BEEM threshold voltage compared to reference Au/GaAs diodes. The energy dependent electron transmission properties of TiOPc were investigated too. Additionally, an approach for the determination of the attenuation length of TiOPc as a function of energy has been successfully...