Si/Al2O3/ZnO:Al capacitor arrays formed in electrochemically etched porous Si by atomic layer deposition

High surface area Si/Al2O3/ZnO:Al capacitors were formed in electrochemically etched porous silicon. The Al2O3 dielectric and the ZnO:Al top electrode were deposited by atomic layer deposition in high aspect ratio porous Si. A single capacitor with a typical area of about 1 mm2 consisted of about 105 pores. Effective capacitance densities were between 2.0 and 2.5 μF/cm2, i.e., approximately 30 times higher than for a planar capacitor prepared under identical conditions, illustrating the effect of the enhanced surface area in the porous structure.