Integration of GaAsP based III-V compound semiconductors to silicon technology

This thesis examines the integration of GaAsP based III-V compound semiconductors to silicon technology using two different concepts: the monolithic growth of GaP and the vapor-liguid-solid (VLS) growth of GaAs nanowires (NWs). Sample fabrication was performed by metalorganic vapor phase epitaxy. It was observed that the growth of GaP needs to be started at low temperatures to obtain a layer-by-layer growth mode. AFM examinations indicated that careful surface preparation prior to the growth is crucial. GaAs NWs were crystallized in the zinc-blende crystal structure and it was observed that the VLS growth method enables the fabrication of GaAs NWs on silicon and even on amorphous low-cost substrates. The growth and characterization of Ga(As)PN alloys, with the composition nearly lattice-matched to silicon, was examined by various methods and it was observed that nitrogen incorporation complicates the growth process. Formation of a misfit dislocation network in the GaP0.98N0.02/GaP interface occurred when the film thickness was about 200 nm. The nitrogen incorporation efficiency was extremely low and it was observed that the amount of nitrogen related point defects increased with the nitrogen content. However, raman scattering and X-ray diffraction measurements implied that the nitrogen incorporation enables the fabrication of GaP based strain compensated structures on silicon substrates. The effect of nitrogen incorporation on the energy band structure of GaAsPN was studied by photoluminescence (PL) and photoreflectance (PR) measurements. The different locations of PL and PR transitions suggested the PL signal to originate from the states related to nitrogen clusters. Furthermore, the conduction band splitting of GaAsPN alloys was observed by the PR measurements. Diodes fabricated from this material were chracterized to gather information from the absorption properties of the material. The photocurrent spectra revealed transitions from the split conduction band and the use of this type of structure in different solar cell devices was discussed. The surface passivation of GaAs was studied fabricating a high-k metal insulator semiconductor capacitors from GaAs with an insulator stack comprised of an AlN surface passivation layer and a high-k HfO2 layer. The Fermi level unpinning in the interface was shown by capacitance-voltage and current-voltage measurements.