Date of Graduation

8-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Graduate School

Advisor

Shui-Qing Yu

Committee Member

Simon Ang

Second Committee Member

Hameed Naseem

Third Committee Member

Kenneth Vickers

Fourth Committee Member

Gregory Salamo

Keywords

Light Detection Devices, Metallic Nanostructures, Nanofabrication

Abstract

Metallic nanostructures have been investigated with various applications especially for integration with light detection devices. The incident light can be manipulated by those nanostructures to enhance light absorption therefor improve device performance. However, previous studies focused on optical design. The electrical properties of these integrated light detection devices have not been fully considered. The photon generated carriers transport and collection are critical for light detection devices as well. An optimized device platform considering from both the optical and electrical aspects to fully utilize these nanostructures is highly desired for future light detection devices.

This dissertation targeted on three objectives, beginning with the fabrication process development of various nanostructures on different substrates. High quality nanostructures were achieved with minimum 20nm gap and 45nm line width. The second objective was developing the metallic fishnet nanostructures integrated Schottky contact a-Si solar cell to improve both light absorption and photon generated carrier collection. The fishnet was designed as the light trapping structure and 2D connected top contact to collect carriers. The third objective was developing metallic nanostructures integrated GeSn photodetectors. The H shape nano antennas were integrated on GeSn photodetectors. Multiple resonant absorption peaks at infrared range were observed using spectroscopic ellipsometry. However, there was no obvious photoresponse value improvement of developed solar cells and H shape antennas integrated GeSn photodetectors. For further investigation, interdigitated electrodes integrated GeSn photodetectors were designed. With less carrier transit time, the responsivity value of the integrated Ge0.991Sn0.009 photodetector was 72µA/W at 1.55µm at room temperature which was 6 times higher comparing to device without integration. Meanwhile, with the increased carrier life time by decreasing temperature, the responsivity value of integrated Ge0.93Sn0.07 detectors at 1.55µm at 100K was 8.5mA/W which was 200 times higher than the value at 300K. These results suggest relative large surface recombination rate was the dominant loss mechanism in metallic nanostructures integrated light detection devices, as the ratio of carrier life time and transit time determines the gain of photodetector. The light detection devices integrated with metallic nanostructures can be developed to maximize device performance with light trapping effect and carrier collection efficiency.

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