Development of Novel Semiconductor Materials and Type-II Heterostructures for Infrared Applications
Creators: name: Duffy, Dominic Andrew
Publisher: name: University of Surrey
Year: 2023

description: With the increasing demand for data-intensive applications, developing higher efficiency and
description: more thermally stable near-infrared semiconductor lasers is of significant interest for the future
description: of telecommunications. A key design consideration for these lasers is the temperature sensitivity
description: of both the output power and emission wavelength, which necessitates using energy-intensive
description: active cooling to stabilise device operation. Removing the need for active cooling would result
description: in improved wall-plug efficiency and reduce the complexity and cost of these devices. This
description: thesis explores the possibility of using new approaches to improve the temperature stability of
description: semiconductor lasers, such as the use of type-II active regions, in which the electrons and holes
description: are spatially separated, and by incorporating highly mismatched bismide and nitride alloys into
description: the active region.<br>
description: <br>
description: GaInAs/GaAsSb type-II ""W""-lasers emitting at 1255 nm were first investigated. These demonstrated low room temperature threshold current densities around 200–300 A/cm2 and a reduced
description: thermal redshift of the emission wavelength around 0.31 nm/K. This reduced thermal redshift was
description: further investigated using temperature-dependent gain studies, supplemented by a comprehensive
description: modelling investigation, which together demonstrated the significant role of injection-dependent
description: electrostatic effects on the temperature sensitivity of type-II active regions. This also resulted in
description: the development of a general-purpose device modelling toolkit.<br>
description: <br>
description: Beyond changing the geometry of the active region, highly mismatched bismuth-containing
description: alloys offer the possibility of suppressing intrinsic non-radiative Auger processes. In this thesis,
description: photoreflectance studies of bismide-nitride alloys were used to quantitatively determine the
description: compositions of both bulk and quantum well structures, and provided an improved understanding
description: of the growth constraints of these interesting alloys.<br>
description: <br>
description: Finally, combining the activities on both novel heterostructures and materials, the prospect of
description: using ""W""-active regions to integrate dilute bismide and nitride alloys was explored, illustrating
description: how this approach could further extend the accessible wavelength range and work towards
description: mitigating the effects of unfavourable Auger losses on device performance.<br>
description: <br>
description: Overall, these results provide an improved understanding of the unique factors and considerations
description: at play in type-II systems and highlight the prospect of exploiting these systems to design devices
description: with a tailored temperature sensitivity, which may lead to improvements in the overall efficiency
description: and thermal stability of near-infrared semiconductor lasers.<br>