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Title: The development and optimization of potential germanium on silicon single photon avalanche diodes
Author: Allred, Phil
ISNI:       0000 0004 5923 9294
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2016
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The work presented in this thesis explores a potential single photon detection technology using Silicon and Germanium, and a possible direction for the future. Instead of the more commonly used III-V materials, the desirable characteristics of each of the Group IV materials is implemented in designing a separate absorption and multiplication region device. Key structural features of the device are investigated and optimised, so that single photon detection in the near infrared is made possible. Growth of these layers is performed using an RP-CVD system, the ultimate industry tool in this field of research. Doping profiles and smooth crystalline growth is implemented using a range of techniques, to produce suitable epitaxial structures which are ideal for further fabrication. Several techniques are used to ensure that the quality of these layers are fully optimised. This optimisation work has resulted in the first single photon detection at a wavelength of 1550 nm, and has also brought the Silicon and Germanium device onto a comparable level to their III-V counterparts at 1330 nm. The superior repetition rate of these Group IV devices also holds an advantage over those designed using InGaAs/InP. The boron doping of Silicon has also been investigated. It has been shown that fully crystalline Silicon boron layers can be produced with boron concentrations (4.5x1020 cm-3) that are higher than their solubility limit at 700oC. The reproducibility of these layers, along with quick turnaround, offers an excellent possibility for industrial use, with a significant advantage over other competing growth techniques. In relation to the work on the single photon detection devices, these B-doped layers offer an interesting etch resistant capability. Suspended structures (wires and membranes) have been produced and characterized using synchrotron measurements. Layers have shown small levels of strain, similar to structures made using Germanium, but overall exhibit a flat platform for further growth. This has led to the idea that suspending a single photon detector that incorporates a reflective mirror could enhance detection efficiency.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics