Band structure engineering of III-V semiconductor compounds with increased wavelength tunability for photonic applications

: Optimisation of semiconductor compounds with increased energy efficiency

Abstract

The exponential growth of the internet mandates the development of energy-efficient “green” photonics technologies. Currently, tele- and data-com laser technology is centred on quantum well (QW) lasers grown on InP. Despite their widespread deployment, and the improvements in efficiency enabled by QW band structure engineering, strong non-radiative losses, and inter-valence band absorption (IVBA) in InP-based 1.3-1.55 µm QW lasers remains a persistent issue. At room temperature, up to 80% of the threshold current density is due to Auger recombination (AR). The strong temperature sensitivity of AR creates a threshold current density with strong temperature dependence. These properties mandate temperature control via thermoelectric coolers to maintain operational stability, thereby increasing power consumption. There is a long-standing goal to develop 1.3-1.55 µm semiconductor lasers in which AR and IVBA are suppressed, creating energy-efficient, temperature-stable lasers.
Significant research has centred on extending the wavelength range accessible to GaAs-based lasers towards the 1.3-1.55 µm tele- and data-com windows. GaAs-based QW lasers incorporating strained In_yGa_1−yAs QWs are already well established at wavelengths close to 1 µm. Extending the wavelength range associated with GaAs-based lasers to 1.55 µm offers significant advantages over incumbent InP-based technologies, including enhanced band offsets and refractive index contrast for improved carrier and optical confinement, the potential to exploit the benefits associated with vertical-cavity architectures, and potential integration with GaAs-based microelectronics. Critical thickness limitations preclude the growth of strained In_yGa_1−yAs QWs and thus unconventional material systems must be considered to target long-wavelength GaAs-based QW lasers. These unconventional material systems include QWs formed using highly-mismatched dilute nitride or bismide alloys with type-I band offsets, metamorphic QWs based on lattice-mismatched Al_xIn_yGa_1−x−yAs QWs with type-I band offsets grown on relaxed In_zGa_1−zAs buffer layers, and “W” QWs with type-II band offsets and based on conventional In_yGa_1−yAs/GaAs_1−xSb_x or highly-mismatched GaAs_1−xBi_x/GaN_yAs_1−y alloys.

Date of Award	24 Jan 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Judy Rorison (Supervisor) & Edmund G H Harbord (Supervisor)