Single and Triple Insulator Tunnel Rectifiers for Infrared Energy Harvesting

Metal Insulator Metal (MIM) and MI ³ M rectifiers have been fabricated by atomic layer deposition (ALD) to investigate the insulator (Al 2 O 3 , Ta 2 O 5 , Nb 2 O 5 ) layer quality and rectification performance for inclusion in rectenna arrays for infrared energy harvesting. ALD has provided superior control of nanometre film thickness (1 to 3 nm) as well as insulator film quality as tunnelling has been found to be the dominant conduction mechanism for all fabricated devices. The Ti/Al 2 O 3/ Au 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. Engineering tunnel barriers in non-cascaded (Ta 2 O 5 /Nb 2 O 5 /Al 2 O 3 ) and cascaded (Nb 2 O 5 /Ta 2 O 5 /Al 2 O 3 ) triple insulator configurations, has been found to shift the onset of rectification reversal from 0.35 V to 1.1 V. A superior low-voltage asymmetry of 6 at 0.1 V and responsivity of 4.3 A/W at 0.35 V are demonstrated for the MI ³ M diode in non-cascaded configuration.