PhD defence by Alisha Nanwani

Abstract

Modern technologies such as faster internet, energy-efficient data centers, and secure communication systems rely on materials that can generate and control light with very high precision. One promising approach is to combine traditional silicon, which is the foundation of today’s electronics, with advanced light-emitting materials known as IIIV semiconductors.

This thesis explores three approaches to bridge that gap by integrating light-emitting materials with silicon. First, it demonstrates how tiny semiconductor crystals, known as quantum dots, can be grown directly on silicon. These nanostructures emit light in the telecommunications band and even show quantum dot–like properties suitable for secure quantum communication. Second, it presents the development of ultra-compact NanoLEDs, which are promising candidates for chip-to-chip optical communication because they can act as fast, efficient light sources at the nanoscale. Finally, it introduces tunnel epitaxy, a novel growth method designed to reduce defects when combining mismatched materials, improving the overall quality and performance of integrated devices.

Together, these advances show practical routes toward silicon chips that not only compute but also generate and control light. Such progress could transform data transfer, reduce the energy cost of information technology, and open the door to new applications in quantum science.

Supervisors

• Principal supervisor: Senior Researcher Elizaveta Semenova, DTU Electro, Denmark
• Co-supervisor: Professor Kresten Yvind, DTU Electro, DenmarkCo-supervisor: Postdoc Pawel Holewa, DTU Electro, Denmark

Evaluation Board

• Professor Nini Pryds, DTU Energy, Denmark
• Professor Jonas Johansson, Lund University, Sweden
• Senior engineer Heinz Schmid, IBM, Switzerland

Master of the Ceremony

• Senior researcher Mikkel Heuck, DTU Electro, Denmark