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Physics Chat

Two approaches to enable III-V/Si integration: quantum dots and tunnel epitaxy

Speaker: Bogdan Ratiu (QLi)
Date: Friday 8 October 2021
Time: 15:00
Venue: Zoom

The silicon manufacturing industry has reached impressive milestones during the last few years, both in terms of electrical and optical circuits. However, the Si platform is starting to reach a plateau in terms of miniaturization. Compound semiconductors have shown many favourable optical and electrical properties that can help continue the miniaturization trend. For large scale manufacturing, the most economically efficient method of integrating III-V compounds with Si is done by direct epitaxy. Epitaxial integration poses challenges such as large lattice mismatch, polarity mismatch and thermal expansion coefficient mismatch. We explore two methods of dealing with the defects created by these mismatches: creating defect resistant structures (quantum dots) and creating defect trapping structures (tunnel epitaxy). Quantum dots (QDs) are nanostructures that confine carriers in all directions. They provide excellent gain material for lasers, having achieved record threshold current, temperature invariance and carrier dynamics. Their resistance to defects makes them ideal candidates for an epitaxially integrated laser. In this talk, I will present the challenges and progress on 1.55 Ám C-band QD lasers grown on silicon by metal-organic chemical vapor deposition (MOCVD). The objective of the research is to offer a key optoelectronic component for a range of applications including long distance fibre optics communication, eye-safe LIDAR, and gas and medical sensing. Tunnel epitaxy is an emerging growth technique allowing large-area, defect-free III-V layers on silicon on insulator (SOI) substrates. The challenges of this method include the complex fabrication of the nano-scale three-dimensional growth patterns, precise control of the nano-epitaxy process and diffusion length limitations. In this talk, I will present the concept of tunnel epitaxy as well as our recent progress of GaAs tunnel epitaxy on the buried silicon surface of around one micron length.

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