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Piezoelectric field and confinement effects on the dielectric function spectrum of InGaN/GaN quantum wells

Einfluß von piezoelektrischen Feldern und "quantum confinement" auf den spektralen Verlauf der dielektrischen Funktionen von InGaN/GaN Quantenfilmen
 
: Ramakrishnan, A.; Wagner, J.; Kunzer, M.; Obloh, H.; Köhler, K.

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Applied Physics Letters 76 (2000), No.1, pp.79-81
ISSN: 0003-6951
ISSN: 1077-3118
English
Journal Article
Fraunhofer IAF ()
group III-nitrides; InGaN/GaN quantum wells; InGaN/GaN Quantenfilme; dielectric function; spectroscopic ellipsometry; spektroskopische Ellipsometrie

Abstract
In(0.13)Ga(0.87)N/GaN double heterostructures and quantum wells (QWs) have been studied by room-temperature photoluminescence (PL) and spectroscopic ellipsometry (SE). PL revealed the presence of strong piezoelectric fields, which strongly influence the luminescence properties for InGaN QW widths in the 3-12 nm range. The pseudodielectric function spectrum derived from the SE measurements were analyzed using a multilayer approach, describing the dielectric function of the individual layers by a parametric oscillator model. The fundamental band-gap resonance in the InGaN dielectric-function spectrum was found to broaden for an InGaN layer width of 12 nm, as compared to bulk-like InGaN layers, due to piezoelectric field effects. For a much narrower QW width of 1.7 nm, however, quantum confinement was found to dominate over piezoelectric-field effects, resulting in a much sharper band-gap resonance shifted to higher energies and an increased oscillator strength.

: http://publica.fraunhofer.de/documents/N-1203.html