Terahertz Response of Semiconductor 2D-electron gas device
Author
Schmidt, Simon Tankred Karkov
Term
3. term (FYS9)
Education
Publication year
2020
Abstract
Motivated by the growing availability of terahertz sources and applications, this thesis develops a physics‑based model of the terahertz response of a two‑dimensional semiconductor structure (2D electron gas) in a layered configuration. The work first establishes the theoretical foundation using Maxwell’s equations and Fresnel reflection/transmission for single and multilayer interfaces, then computes guided modes in a related structure to inform initial and boundary conditions. Building on this, a Green’s function formulation for a scatterer on a layered semiconductor is derived and implemented (calculations carried out in Matlab). The resulting model yields usable terahertz response predictions, but practical memory constraints prevent increasing the discretization to resolutions that ensure stable convergence; accordingly, the results should be treated as qualitative guidance rather than definitive design data. The guided‑mode analysis also explores parameter variations (e.g., dielectric properties, air or perfect conductor as the top layer, and magnetic field) to contextualize the modeling assumptions.
Motiveret af den voksende tilgængelighed af terahertz‑kilder og anvendelser udvikler denne afhandling en fysikbaseret model for terahertz‑responsen af en todimensional halvlederstruktur (2D‑elektrongas) i en lagdelt geometri. Først opstilles det teoretiske grundlag med Maxwells ligninger og Fresnel‑refleksion/-transmission for enkelt- og flerlagsgrænseflader, hvorefter ledte modes i en beslægtet struktur beregnes for at fastlægge start- og randbetingelser. På dette grundlag udledes og implementeres en Green’s‑funktions‑formulering for en spreder på en lagdelt halvleder (beregningerne udført i Matlab). Modellen giver brugbare forudsigelser af terahertz‑responsen, men praktiske hukommelsesbegrænsninger forhindrer at øge diskretiseringsopløsningen til et niveau, der sikrer stabil konvergens; derfor bør resultaterne betragtes som vejledende frem for endelige designdata. Analysen af ledte modes undersøger desuden parametervariationer (fx dielektriske egenskaber, luft eller perfekt leder som øverste lag samt magnetfelt) som kontekst for modellens antagelser.
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