This thesis describes the growth and structural characterization of epitaxial 2h­ A1_1-xIn_xN ranging from pure A1N to InN [0<x<1]. Thin A1_1-xIn_xN films were synthesized by dual DC reactive Magnetron Sputter Epitaxy (MSE) in an ultra-high vacuum (UHV) system. Growth parameters such as deposition temperature and magnetron power settings were adjusted in order to control the film stoichiometry. The role of in-situ deposited TiN(111) and ZrN(111) seed layers on the A1_1-xIn_xN growth was also investigated. It was found that ZrN(111) seed layers provide a wider stoichiometric composition region at elevated temperatures due to its low lattice mismatch as compared to TiN(111). Microstructural characterization of A1_1-xIn_xN deposited at temperatures from 300 to 900 °C was carried out by X-ray diffraction (XRD) techniques and transmission electron microscopy (TEM). TEM micrographs revealed a dense and columnar microstructure with column widths ranging from 10 to 200 nm depending on growth temperature and seed layer. In addition, a novel generic growth mode giving rise to extremely curved, though stress- free, crystal lattices was observed and investigated. It was found that these, so called, nano-grass structures arise due to specific kinetic and geometrical limitations during growth. Compositional differences are formed over the columns due to self-shadowing effects, which are partly preserved due to the low surface ad-atom mobility. Thus resulting in extremely curved crystalline columns. XRD investigations showed that single-phase wurtzite epitaxial A1_1-xIn_xN was obtainable throughout the whole composition range for deposition temperatures of up to 600 °C onto ZrN(111) seed layers. At higher temperatures almost pure hexagonal A1N was formed. XRD and selected area electron diffraction also showed that the A1_1-xIn_xN films were grown hetero-epitaxially onto TiN and ZrN with the epitaxial relationship: A1_1-xIn_xN(0001)//TiN(ZrN)(111) and A1_1-xIn_xN[10-10]//TiN(ZrN)[110]. In the case of A1_1-xIn_xN depositions onto TiN(111) seed layers, a phase separation of A1_1-xIn_xN was observed when mid-x compositions was targeted at deposition temperatures of 600 °C. This observation was confirmed by TEM results, which revealed a layered structure with epitaxial 2h-A1_1-xIn_xN followed by a nano-crystalline structure. Based on the results, pseudo-binary phase diagrams for MSE deposition of 2h-A1_1-xIn_xN, at temperatures up to 1000°C, onto TiN(111) and ZrN(111) coated MgO(111) could be established.