Subbandgap Photoluminescence and Electroluminescence at n-GaN Electrodes in Aqueous Solutions

Huygens, Inge; Gomes, W. P.; Theuwis, Antoon; Strubbe, Katrien

doi:10.1149/1.1603251

Cited by 4 publications

(9 citation statements)

References 9 publications

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“…In our previous paper on galvanostatic EL measurements at n-GaN/sapphire electrodes, 4 we observed almost no dependence of the spectral distribution on the electrode potential for electrodes that were not etched, contrary to the potentiostatically obtained results presented in this paper. Different effects may account for these apparent contradictions.…”

Section: G74contrasting

confidence: 99%

“…As discussed in Ref. 4, a value for the PL intensity at flatband conditions larger than I PL 0 does not affect the slope ͑i.e., the value for ␣͒ but leads to a positive intercept on the ordinate axis in a ͓−ln͑I PL /I PL,max ͒ vs W depl ͔ plot. A possible explanation for the fact that I PL,max is larger than I PL 0 is that at V FB , the conditions set in the Gärtner model are not fulfilled.…”

Section: G74mentioning

confidence: 75%

“…PL measurements at n-GaN/sapphire electrodes were already described thoroughly in Ref. 4. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In a previous paper, 4 we reported sub-bandgap photoluminescence ͑PL͒ and electroluminescence ͑EL͒ measurements at n-GaN electrodes grown on sapphire substrates. When comparing PL and EL measurements, indications were found that sub-bandgap EL partially originates from ͑near͒ surface states.…”

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confidence: 99%

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Defect Luminescence at n-GaN Electrodes

Huygens

Gomes

Strubbe

2006

J. Electrochem. Soc.

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Luminescence measurements in aqueous solutions were performed upon n-GaN layers grown on sapphire substrates and on Si substrates. Photoluminescence ͑PL͒ measurements at n-GaN/sapphire and n-GaN/Si electrodes show an identical emission band centered at 2.20 eV ͑the well-known yellow luminescence band͒, showing that the same deep acceptor level is present in both materials. Additional reddish luminescence is observed when the holes are injected from the solution ͓electroluminescence ͑EL͔͒, which may be ascribed to the occurrence of radiative ͑near͒ surface recombination. From an analysis of the potential dependence of both the PL and EL intensity of the 2.20-eV band, it may be concluded that this band possesses a significant contribution from the ͑near͒ surface.

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Section: G74contrasting

confidence: 99%

Section: G74mentioning

confidence: 75%

“…PL measurements at n-GaN/sapphire electrodes were already described thoroughly in Ref. 4. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Defect Luminescence at n-GaN Electrodes

Huygens

Gomes

Strubbe

2006

J. Electrochem. Soc.

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“…31 In the case of GaN, photoanodic etching was reported to take place in sulfuric acid and in alkaline solutions, but to a minor extent only in 1 mol L Ϫ1 HCl. 12,32 Hence, photoanodic etching in HCl solution may constitute a way of selectively removing In x Ga 1Ϫx N from GaN/In x Ga 1Ϫx N multilayer structures. Alternatively, it should be possible to selectively etch In x Ga 1Ϫx N with respect to GaN by an appropriate choice of the incident light.…”

Section: Discussionmentioning

confidence: 99%

A Photoelectrochemical Study of In[sub x]Ga[sub 1−x]N Films

Theuwis

Strubbe

Depestel

et al. 2002

J. Electrochem. Soc.

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The III-nitride semiconductor n-In x Ga 1Ϫx N was investigated by optical absorbance and luminescence measurements and by various photoelectrochemical methods. Evidence is found for the presence of localized states and compositional fluctuations. Upon illumination with the appropriate wavelength and positive polarization in an indifferent electrolyte, i.e., aqueous 1 mol L Ϫ1 HCl, photocurrent flow is observed, resulting in the photoanodic etching of the solid. Measurements of the quantum efficiency Q and the transient photocurrent show that recombination of photogenerated charge carriers competes effectively with photoanodic dissolution.In the last decade, III-nitride materials such as GaN and In x Ga 1Ϫx N have been the subject of a considerable amount of research. Although the layers grown by metallorganic vapor-phase epitaxy ͑MOVPE͒ generally contain a large quantity of defects, highbrightness light-emitting diodes ͑LEDs͒ with excellent operating lifetimes as well as blue and violet laserdiodes, based upon these materials, are commercially available. 1,2 In the specific case of MOVPE-grown In x Ga 1Ϫx N layers, it has been demonstrated that indium is incorporated in the In x Ga 1Ϫx N lattice in an inhomogeneous way. 3-7 These fluctuations in composition may lead to substantial fluctuations in the bandgap energy E g of the alloy. Moreover, both extended and point defects are generally present in the alloy. 1,8 The aim of this study is to gain insight into the defect structure of this material. The use of ͑photo͒electrical characterization techniques such as photocurrent spectroscopy would require the formation of a high-quality rectifying semiconductor/metal contact. 9 However, to date little work has been done on the formation of good Schottky contacts on In x Ga 1Ϫx N. 10 In the present case, a semiconductor/electrolyte contact may constitute an elegant alternative to a semiconductor/metal contact for such studies.Despite the large amount of research done on III-N compoundbased optoelectronic devices, no suitable wet etchant has been found yet for In x Ga 1Ϫx N. 11 A photoelectrochemical study of the III-nitride/ electrolyte junction can also provide valuable information on the wet-etching behavior of this material. For GaN, such a study has already been conducted, both the photoanodic dissolution reaction and the open-circuit photoetching of GaN being investigated. 12 As in the case of In x Ga 1Ϫx N, no such study has to our knowledge been reported, so we have also performed this type of measurement in the present case. ExperimentalThe In x Ga 1Ϫx N films were grown by MOVPE at the Department of Information Technology at Ghent University. The In x Ga 1Ϫx N epi layers ͑x ϭ 0.21, to be discussed further, average thickness 1 m, unintentionally doped n-type͒ were grown on top of a structure consisting of a GaN epi layer, a 60 nm thick undoped GaN buffer layer, and a 350 m thick ͑0001͒ sapphire substrate.For details on the electrochemical measuring equipment and the electrode fabrication, see Ref. 12. Illuminati...

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