Nanocrystalline Silicon Diodes for Rectifiers on Flexible RFID Tags

Abstract

ABSTRACTThere has been an on-going effort to produce low cost radio frequency identification (RFID) tags as a replacement for traditional barcodes. One method to achieve low cost production is to integrate the manufacturing of the substrate, antenna and active devices into one single continuous process. Hydrogenated nanocrystalline silicon (nc-Si:H) is a suitable material for manufacturing the active devices in such a process.We present a nc-Si:H diode suitable for use in rectifiers on RFID tags. It consists of a Cr bottom contact, an undoped layer of nc-Si:H, an n-doped nc-Si:H and an Al top contact. We demonstrate the current-voltage characteristics of the nc-Si:H diode are much improved over a-Si:H diodes. Current density of 10 A/cm2 and ON/OFF ratio greater than 106 was measured at 2 V forward bias. Output DC voltage of 2.6 V was achieved using four nc-Si:H diodes in a full-wave bridge rectifier. The input AC signal was a sine wave at 14 MHz and 2 VRMS amplitude.