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Author:Kivisaari, Pyry
Title:The effect of current injection geometry on current spreading in semiconductor LEDs
Injektiogeometrian vaikutus sähkövirran jakautumiseen puolijohdeledeissä
Publication type:Master's thesis
Publication year:2010
Pages:[8] + 62      Language:   eng
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Laskennallinen tekniikka   (S-114)
Supervisor:Tulkki, Jukka
Instructor:Oksanen, Jani
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201203131552
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  873   | Archive
Keywords:solid state lighting
light-emitting diodes
nitride semiconductors
thin-film flip-chip LEDs
transverse multi-quantum well LEDs
efficiency
numerical modeling
FEM
puolijohdevalaistus
ledit
nitridipuolijohteet
TFFC-ledit
TJM-ledit
hyötysuhde
numeerinen mallinnus
FEM
Abstract (eng): In this thesis the physical models needed in simulating the operation of semiconductor LEDs are reviewed and used to numerically model the operation of two different LED structures.
The numerical models are solved with the finite element method and the simulated structures are variations of the thin-film flip-chip and transverse multi-quantum well LEDs which are recently proposed structures for efficient white light generation.

The numerical models used in this thesis are based on Maxwell's equations, Fermi-Dirac statistics, semiconductor current equations and basic recombination models.
Modelled materials are nitride semiconductors which exhibit strong spontaneous and piezoelectric polarization fields, and these fields are also included in the models.

The two above mentioned LED structures are compared with each other in terms of the current injection properties, overall efficiency, light output power and the frequency distribution of the generated light.
The effect of the current injection layer width on the efficiency is studied as well.
In addition, the effect of the spontaneous and piezoelectric polarization fields on the LED operation and efficiency is investigated.
Abstract (fin): Diplomityössä esitellään ledien toiminnan kuvauksessa käytettyjä fysikaalisia malleja sekä mallinnetaan kahden valitun ledirakenteen toimintaa numeerisesti.
Mallit ratkaistaan käyttämällä hyväksi elementtimenetelmää.
Mallinnettavat ledirakenteet perustuvat TFFC- ja TMJ-ledeihin, jotka on hiljattain esitelty tieteellisessä kirjallisuudessa tehokkaina valaistusledirakenteina.

Diplomityössä käytetyt numeeriset mallit perustuvat Maxwellin yhtälöihin, Fermi-Dirac-statistiikkaan, puolijohteiden virrankuljetusyhtälöihin ja yleisiin rekombinaatiomalleihin.
Työssä mallinnetaan nitridipuolijohteita, joissa esiintyy voimakkaita spontaaneja sekä pietsosähköisiä polarisaatiokenttiä, ja näiden kenttien vaikutus on huomioitu työssä käytetyissä malleissa.

Työssä verrataan yllämainittuja ledirakenteita toisiinsa tutkimalla sähkövirran injektiota, ledien hyötysuhdetta, säteilevän valon tehoa sekä säteilevän valon taajuusjakaumaa.
Työssä tutkitaan myös virranlevityskerroksen leveyden vaikutusta rakenteiden tehokkuuteen.
Lisäksi tarkastellaan spontaanin ja pietsosähköisen polarisaation vaikutusta ledien toimintaan ja hyötysuhteeseen.
ED:2010-11-26
INSSI record number: 41363
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