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Optical observation of discrete well width fluctuations in wide band gap III‐nitride quantum wells
Author(s) -
Haratizadeh H.,
Monemar B.,
Paskov Plamen P.,
Holtz Per Olof,
Valcheva E.,
Persson P.,
Iwaya M.,
Kamiyama S.,
Amano H.,
Akasaki I.
Publication year - 2007
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200675106
Subject(s) - photoluminescence , full width at half maximum , exciton , quantum well , excitation , spectral line , condensed matter physics , lattice constant , nitride , metalorganic vapour phase epitaxy , spectral width , lattice (music) , monolayer , chemistry , molecular physics , materials science , physics , optics , wavelength , laser , epitaxy , nanotechnology , layer (electronics) , quantum mechanics , astronomy , diffraction , acoustics
A detailed observation of discrete well width fluctuations via localized excitons in the photoluminescence (PL) spectra of MOCVD‐grown undoped GaN/Al 0.07 Ga 0.93 N multiple quantum wells (MQWs) has been reported. Doublet excitonic features with a distance varying between 10 and 25 meV for different well widths (1.5 to 4.5 nm) are observed in the PL spectra. They are explained in terms of discrete well width variations by one c ‐lattice parameter, i.e. two GaN monolayers. By mapping the PL measurements across the samples with different excitation spot size, it is shown that the extension of areas with a constant well width is less than 1 μm 2 . TEM pictures give evidence of interface roughness, although the contrast is weak at this low Al composition. In addition we observe a long‐range variation of the PL peak position across the sample, interpreted as a fluctuation in Al composition in the barriers. The residual broadening of an excitonic peak (apart from the splitting related to well width fluctuations) is about 10 meV, somewhat larger for larger well widths, and is mainly ascribed to hole localisation potentials in the QWs. Additional broadening occurs in the MQWs due to inequivalent properties of each QW within the excitation spot. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)