Aluminum doped ZnO (AZO) has been deposited on (100), (110) and (111) oriented n-type Si and on fused silica by atomic layer deposition (ALD). The films have been post deposition annealed in the temperature range 200-500 οC. The AZO films have been characterized by X-ray diffraction (XRD), Hall and transmittance measurements. Circular diodes have been fabricated from the AZO/Si structures and characterized by current-voltage (IV) and deep level transient spectroscopy (DLTS). The AZO films form Schottky junctions with the Si substrates for all the crystallographic orientations. It is established that after post deposition annealing the structure AZO/n-Si (110) is distinguished as the system with largest rectification.