Single and triple insulator Metal-Insulator-Metal diodes for infrared rectennas

Tunnel-barrier rectifiers comprising single and triple insulator configurations have been fabricated by atomic layer deposition (ALD) to investigate the insulator (Al2O3, Ta2O5, Nb2O5) layer quality and rectification performance for inclusion in rectenna arrays for infrared energy harvesting. ALD has provided superior control of nanometer film thickness (1-3 nm) as well as insulator film quality as tunneling has been found to be the dominant conduction mechanism for all fabricated devices. The key rectifier properties, such as asymmetry, nonlinearity, responsivity and dynamic resistance have been assessed from current-voltage (I-V) measurements. The Au/Al2O3/Ti diode exhibits zero bias responsivity of -0.6 A/W, showing that it can be used for energy harvesting applications without the aid of external bias. The effect of resonant tunneling on rectification performance of triple insulator non-cascaded (Ta2O5/Nb2O5/Al2O3) and cascaded (Nb2O5/Ta2O5/Al2O3) rectifiers has been observed from experimental I-V characteristics and substantiated by theoretical simulations. Superior lowvoltage asymmetry (6 at 0.1 V) and responsivity (4.3 A/W at 0.35 V) for triple insulator MI3M rectifiers have been observed. The resonant tunneling does not provide enhanced rectification at low bias as previously reported, rather it has much smaller effect. The latter indicates that dissimilar metal electrodes rectifier configurations are more promising for inclusion in optical rectenna.