Thesis
Heterogeneous integration of ZnCdSe/ZnCdMgSe vertical-external-cavity surface-emitting laser heterostructures
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T16898
- Person Identifier (Local)
- 201763965
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The wide bandgap ZnCdMgSe-on-InP material system offers the opportunity to develop vertical-external-cavity surface-emitting lasers (VECSELs) with a fundamental emission at typically hard to reach visible wavelengths (540 nm – 590 nm). This thesis reports the progress towards the development of this novel laser system. The material parameters of the ZnCdMgSe-on-InP material system are less studied than their more mature III-V counterparts and so in this work a literature review is conducted and a list of all parameters necessary to design a ZnCdMgSe-based VECSEL are summarized. A simple model of the material gain of a ZnCdSe/ZnCdMgSe quantum well (QW) is assessed and used to inform an analysis, based on that proposed by Kuznetsov for infrared VECSELs [1], to calculate the optimum gain structure design for a 565 nm emitting ZnCdMgSe-based distributed-Bragg-reflector-free (DBR-free) VECSEL. The optimum structure consisted of 4 pairs of ZnCdSe/ZnCdMgSe QWs, spaced with a resonant periodic gain arrangement. The molecular beam epitaxial growth of this structure is completed and multiple growth campaigns are used to iteratively improve the material quality by varying the thicknesses of the II-VI and InGaAs buffer layers that are required for growth on InP substrates. ZnCdMgSe DBR-free VECSEL structures need to undergo epitaxial lift off from their native (001) InP substrate, as it is opaque at visible wavelengths. The resulting ZnCdMgSe membranes need to be transferred onto single crystal, high thermal conductivity, intra cavity, transparent heatspreaders such as diamond or silicon carbide (SiC) to achieve efficient thermal management. A full substrate removal method is developed to yield cm2 sized QW membranes, which are subsequently broken into pieces and bonded to diamond. The low quality membranes produced by the full substrate removal method did not reach the laser threshold. The low membrane quality is attributed to damage induced by the HCl based wet etching of the InP substrate and the handling of membranes in liquid suspension. Due to the poor results of the full substrate removal a suspension and transfer printing method was developed for the ZnCdMgSe-on-InP material system: 100-μm-sided square membranes held by anchors to rails were patterned into a ZnCdMgSe layer, had sidewall protection applied and were under-etched using a three step wet etch to liberate them from the InP substrate and remove the InGaAs buffer layer. The resulting ZnCdMgSe membranes exhibit nm-scale root mean quare surface roughness and are transfer printed onto diamond, a result which highlights promise for the future heterogeneous integration of the ZnCdMgSe. The same suspension and transfer printing method is adapted to a GaInP/AlGaInP, DBR-free VECSEL structure and used to transfer print DBR-free VECSEL membranes onto diamond. The ZnCdMgSe and GaInP/AlGaInP membranes undergo surface roughness, photoluminescence and Raman spectroscopy characterization, which reveals that sidewall protection and under-etch chemistry improvements are required for transfer printed DBR-free VECSEL membranes to reach threshold.
- Advisor / supervisor
- Hastie, Jennifer
- Resource Type
- DOI
- Date Created
- 2023
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PDF of thesis T16898 | 2024-04-30 | Público | Descargar |