Date of Award

1-1-2018

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

Content Description

1 online resource (ii, ix, 105 pages) : illustrations (some color)

Dissertation/Thesis Chair

Harry Efstathiadis

Committee Members

John W Zeller, Nathaniel Cady, Christopher Hobbs, Hassaram Bakhru

Keywords

Detectors, Germanium, Infrared, p-i-n, Photodetector, Infrared detectors, Germanium diodes, Silicon diodes, Metal oxide semiconductors, Complementary

Subject Categories

Engineering

Abstract

Important factors for infrared photodetectors are that they are high-performing, low-cost devices. The performance can be characterized through the quantum efficiency, speed and device noise. Germanium (Ge) on silicon (Si) offers a comparable alternative to conventional groups III-V infrared detector materials such as InGaAs, InSb and HgCdTe in order to develop near-infrared (NIR) photodetector devices that operate with a high responsivity and a relatively low dark current without being cooled. As a Group IV material, Ge is compatible with Complementary Metal-Oxide-Semiconductor (CMOS) manufacturing which allows for a high-quality, high-throughput device for minimum cost. As a result of a thermally induced biaxial tensile strain incorporated into the Ge film, the bandgap of the Ge is modulated, and the photodetector's absorption range can be increased to even longer wavelengths (1600 nm range). We have used CMOS processes in order to fabricate Ge based p-i-n NIR photodetector devices on 300 mm Si wafers. P-i-n junctions offer many benefits such as the ability to tune the width of the depletion region and a strong built-in electric field (~several kV/cm) which can overcome recombination losses and increase response speed. The Ge is deposited in a two-step process to reduce the dislocation density which could form recombination centers and contribute to a higher dark current. Characterization, including TEM, EDS and SIMS, has been done to ensure a quality, crystalline film. We have also performed electrical testing of the device. The device exhibited strong diode behavior as well as an exceptionally low dark current of 1.35 nA. We have developed a model for these devices using Sentaurus TCAD in order to compare our experimental results with theoretical results. Using this model as a baseline, we have simulated a device of a novel design consisting of a lateral, radial p-i-n junction to simultaneously realize an improved quantum efficiency, optimized speed and decreased device noise. The optimal depletion layer width has also been investigated.

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