| AVS 59th Annual International Symposium and Exhibition | |
| Thin Film | Monday Sessions |
| Session TF-MoM |
| Session: | ALD Enabled Applications |
| Presenter: | O. Ajayi, University of South Florida |
| Authors: | O. Ajayi, University of South Florida G. Mumcu, University of South Florida J. Wang, University of South Florida |
| Correspondent: | Click to Email |
Due to its unique resistive switching capability, Metal-Insulator-Metal (MIM) diodes have attracted substantial interests ever since 1960’s. The early generation of MIM device (point-contact diode) is composed of a sharp metal tip placed right on top of a planar metal electrode coated with an ultra-thin layer of insulator. It has been envisioned that MIM diodes hold great promise for detecting and mixing high frequency signals up to Terahertz (THz) range. Particularly, several prior works have suggested for operation at THz frequencies, the MIM diodes are anticipated to outperform heterojunction diodes, which have limited cutoff frequency (<3THz). Hence, the MIM devices are well-suited for a wide range of applications in security, imaging and energy scavenging. In lieu of this, microfabricated MIM diodes with low zero-bias impedance have been actively pursued in this work for a strategically-designed antenna-coupled detector with high responsivity.
With introduction of ultra-thin tunneling layer sandwiched between two planar metal electrodes, the microfabricated MIM diodes are amenable for direct integration with ICs. In particular, we have devoted most of our efforts on developing techniques to improve the overall diode characteristics through tuning its tunneling properties. The effective junction capacitance and resistance limit the operation frequency range of tunneling diode. The key factors that affect the frequency range of tunneling diodes are the junction area, defect density, permittivity and thickness of the tunneling layer. For the MIM diode, a small deviation in tunneling barrier thickness can cause a significant change in the junction resistance and its I-V responses. Hence, atomic layer deposition (ALD) process was employed which offer superb uniformity, low defect density, and precise thickness control of the tunneling layer. In this work, MIM diodes with a variety of junction areas ranging from 3µm´3µm to 100µm´100µ have been fabricated with different ALD thin films (e.g., TiO2 and HfO2) of varied thicknesses. By systematic investigation of the measured I-V characteristics for MIM devices with a variety of junction materials, junction thickness and junction area, it is evident that the performance of the MIM tunneling diodes can be greatly enhanced through optimizing junction properties (material, thickness, area, etc.). As compared to similar devices reported previously, we have successfully demonstrated high-yield MIM diodes with 1.5nm-thick tunneling junction with unprecedented low junction resistance in the range of 500Ω or even less, thus resulting in greatly enhanced responsivity.