Contactless electromodulation spectroscopy of AlGaN∕GaN heterostructures with a two-dimensional electron gas: A comparison of photoreflectance and contactless electroreflectance

Kudrawiec, R.; Syperek, M.; Motyka, M.; Misiewicz, J.; Paszkiewicz, R.; Paszkiewicz, B.; Tłaczała, M.

doi:10.1063/1.2206707

Cited by 43 publications

(36 citation statements)

References 19 publications

(13 reference statements)

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“…This resonance exhibits Franz-Keldysh oscillation, which is typical of absorption in a bulk-like layer with a strong and homogenious built-in electric field [7]. It is worth noting that such an oscillation is often observed for AlGaN/GaN transistor heterostructures [5]. The builtin electric field in AlGaN layer, extracted from the FKO period [5,7], equals ~0.5 MV/cm.…”

Section: Experiment Results and Discussionmentioning

confidence: 99%

“…It is worth noting that such an oscillation is often observed for AlGaN/GaN transistor heterostructures [5]. The builtin electric field in AlGaN layer, extracted from the FKO period [5,7], equals ~0.5 MV/cm. In addition to AlGaN-related resonance, a weak resonance is observed at the energy of 3.68 eV.…”

Section: Experiment Results and Discussionmentioning

confidence: 99%

“…Recently, a clear experimental evidences for this effect has been provided by contactless electroreflectance (CER) spectroscopy [1], i.e., an absorption-like technique which is insensitive to optical transitions associated with defect-states [2][3][4]. It is worth noting, that the deepness of sample probing by CER spectroscopy is strongly limited for AlGaN/GaN transistor structures due to the screening of elecromodulation by the sheet of two dimensional electron gas (2DEG) at the AlGaN/GaN interface [5,6]. It means, that CER signal originates from the region between the sample surface and the GaNchannel layer.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

GaN Surface Quantum Well In AlGaN∕GaN Transistor Heterostructure Studied By Contactless Electroreflectance

Kudrawiec¹,

Gładysiewicz²,

Misiewicz³

et al. 2010

AIP Conference Proceedings

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Abstract. Contactless electroreflectance (CER) has been applied to study optical transitions in GaN capped AlGaN/GaN transistor heterostructure. In addition to strong AlGaN-related resonance, a clear CER resonance has been observed at the energy of 3.68 eV. This resonance has been attributed to the optical transition within the GaN cap layer which creates a surface quantum well (QW). The confinement energy and the electron-hole overlap integral for the surface QW have been calculated within the electron effective mass approximation. A good agreement between experimental data and theoretical calculations have been found.

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Section: Experiment Results and Discussionmentioning

confidence: 99%

Section: Experiment Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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GaN Surface Quantum Well In AlGaN∕GaN Transistor Heterostructure Studied By Contactless Electroreflectance

Kudrawiec¹,

Gładysiewicz²,

Misiewicz³

et al. 2010

AIP Conference Proceedings

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“…The different relative intensities of the GaNAs− and QW−related signal in CER and PR spectra are also associated with different modulation mechanism in these two techniques. The other effect leading to much smaller deepness of sample probing by CER spectroscopy is the screening phe− nomenon which is typical of heterostructures with the two− −dimensional (2D) electron gas (2DEG) at semiconductor interfaces [66,67]. Figures 20(a) and 20(b) show the PR and CER spectra, respectively, obtained for an AlGaN/GaN heterostructure with a 2DEG at the interface.…”

Section: Contactless Electroreflectance Vs Photo--reflectancementioning

confidence: 99%

“…Similar behaviour has been observed for other AlGaN/GaN heterostructures with the 2DEG at the AlGaN/ GaN interface. It means that some parts of GaN layer are not probed in CER since the 2DEG at the AlGaN/GaN interface screens the modulation of the built−in electric field in GaN layer [66,67]. In other words, it means that due to the high concentration of 2DEG at AlGaN/GaN interface the exter− nal modulation is not able to change band bending in the GaN layer.…”

Section: Contactless Electroreflectance Vs Photo--reflectancementioning

confidence: 99%

Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

Misiewicz

Kudrawiec

2012

Opto-Electronics Review

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The authors present the application of contactless electroreflectance (CER) spectroscopy to study optical transitions in low dimensional semiconductor structures including quantum wells (QWs), step-like QWs, quantum dots (QDs), quantum dashes (QDashes), QDs and QDashes embedded in a QW, and QDashes coupled with a QW. For QWs optical transitions between the ground and excited states as well as optical transitions in QW barriers and step-like barriers have been clearly observed in CER spectra. Energies of these transitions have been compared with theoretical calculations and in this way the band structure has been determined for the investigated QWs. For QD and QDash structures optical transitions in QDs and QDashes as well as optical transitions in the wetting layer have been identified. For QDs and QDashes surrounded by a QW, in addition to energies of QD and QDash transitions, energies of optical transitions in the surrounded QW have been measured and the band structure has been determined for the surrounded QW. Finally some differences, which can be observed in CER and photo-reflectance spectra, have been presented and discussed for selected QW and QD structures.

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Depletion Layer Built‐In Field at (1−100), (0001), and (000−1) GaN/Water Junction and Its Role in Semiconductor Nanowire Water Splitting

Stokowski

Janicki

Serafińczuk

et al. 2019

Adv Materials Inter

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IntroductionFollowing the discovery of semiconductor-based photoelectrolysis by Fujishima and Honda, [1] a considerable attention has been given to this phenomenon as a very promising for clean, sustainable, and storable fuel generation. [2][3][4][5][6] An important aspect of consideration is exploring various kinds of materials and structures to optimize the water-splitting efficiency. The main requirement for the electrode material is a suitable bandgap, which not only allows harvesting the sunlight energyThe nature of specific GaN plane/water interfaces under external bias and illumination can influence photoelectrolysis efficiency using GaN nanowires. Studies of Ga-polar, N-polar, and m-plane GaN interfaces with deionized water allow determining differences between surfaces corresponding to different nanowire facets. They are investigated under external bias conditions to reveal the profile of Fermi level localization through analysis of Franz-Keldysh oscillations using electrolyte electroreflectance (EER) technique in a specially designed measurement chamber. Calculation of the potential barrier height is also possible. EER study shows differences between surface densities of states (SDOS) at distinct GaN planes. One broad SDOS is identified near the conduction band in case of ±c-plane and related to Ga adatom reconstruction and β-Ga 2 O 3 presence at the GaN electrode. Two narrow SDOS singularities are found at the m-plane one of which is localized near the middle of the bandgap and allows to generate approximately two times higher surface potential barrier than in case of polar surfaces at zero-bias conditions. This suggests that n-type GaN nanowires can enhance carrier separation at sidewalls and refine the oxygen evolution rate. Additionally, a voltage-controlled hysteresis loop of Fermi level localization is detected at the Ga-face GaN/water interface.but also is sufficient to overcome overpotentials necessary to split water molecules. One of the most promising materials in this context is gallium nitride, which has been reported useful both as a solid electrode [7] and in a form of nanowire arrays. [8,9] Due to the polar character of the wurtzite crystal structure of GaN, the nature of particular planes in nanowires can differ and result in a change of performance in photoelectrolysis. Especially, the built-in electric field emerging at the surface of GaN brought in a contact with water can have tremendous consequences on photogenerated carriers' separation and their transfer to the surface, where the hydrogen-and oxygen-evolution reactions are driven. The above-mentioned fields and band bending [10] are controlled by the Fermi level pinning at the gallium nitride surface states which are dependent upon the crystal plane choice. [11] In case of wurtzite crystal-based nanowires the most interesting are (0001) c-plane and (1−100) m-plane which usually correspond to the top and side walls of these structures, respectively.Studies of the Fermi level position at semiconductor/water interface can be challeng...

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Contactless electromodulation spectroscopy of AlGaN∕GaN heterostructures with a two-dimensional electron gas: A comparison of photoreflectance and contactless electroreflectance

Cited by 43 publications

References 19 publications

GaN Surface Quantum Well In AlGaN∕GaN Transistor Heterostructure Studied By Contactless Electroreflectance

GaN Surface Quantum Well In AlGaN∕GaN Transistor Heterostructure Studied By Contactless Electroreflectance

Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

Depletion Layer Built‐In Field at (1−100), (0001), and (000−1) GaN/Water Junction and Its Role in Semiconductor Nanowire Water Splitting

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