Scanning Tunneling Luminescence Studies of Nitride Semiconductor Thin Films under Ambient Conditions

Manson-Smith, S.K.; Trager-Cowan, C.

doi:10.1002/1521-3951(200111)228:2<445::aid-pssb445>3.0.co;2-i

Cited by 2 publications

(2 citation statements)

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“…Note that, previous STL microscopy studies in nitride devices showed luminescence intensity fluctuations over a typical scale of 100 nm. In these early experiments, structures were not compatible with high resolution because of thick injection layers (100 nm in [31], 200 nm in [32]) and multiple QW active region [31] or a single QW capped with a GaN/AlGaN barrier [32].…”

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confidence: 99%

Evidence of nanoscale Anderson localization induced by intrinsic compositional disorder in InGaN/GaN quantum wells by scanning tunneling luminescence spectroscopy

et al. 2018

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We present direct experimental evidences of Anderson localization induced by the intrinsic alloy compositional disorder of InGaN/GaN quantum wells. Our approach relies on the measurement of the luminescence spectrum under local injection of electrons from a scanning tunneling microscope tip into a near-surface single quantum well. Fluctuations in the emission line shape are observed on a few-nanometer scale. Narrow emission peaks characteristic of single localized states are resolved. Calculations in the framework of the localization landscape theory provide the effective confining potential map stemming from composition fluctuations. This theory explains well the observed nanometer scale carrier localization and the energies of these Anderson-type localized states. The energy spreading of the emission from localized states is consistent with the usually observed very broad photo-or electro-luminescence spectra of InGaN/GaN quantum well structures.InGaN quantum wells (QWs), the active regions of nitride-based LEDs, display broad photo-or electroluminescence spectra. The emission is assumed to be inhomogeneously broadened due to contributions from material regions with different eigenenergies associated with fluctuations of the In content. Spatial variations of emission intensities and/or energies were previously observed in nitride semiconductor structures by far field [1] and near-field [2, 3] photoluminescence microscopy or cathodoluminescence microscopy [4][5][6]. These observations have evidenced so far emitting domains of either micron or submicron (typically 100 nm) size. While significant energy shifts due to these rather large-scale fluctuations were observed, no linewidths below 100 meV at room temperature were detected. These large-scale luminescence fluctuations are usually associated with growth inhomogeneities seen for instance in AFM. However, in the case of random atom positioning in the alloy crystal [7], modeling predicts that the compositional disorder should induce Anderson localization in regions of a few nm size [8][9][10][11][12][13][14]. Moreover, emission from such single localized states is expected to exhibit a narrow linewidth of a few tens of meV at room temperature, i.e. comparable to what was observed from single GaN quantum dots [15]. Such emission features exhibiting size and spectroscopic signatures characteristic of carrier localization induced by the alloy disorder have not been evidenced up to now.Here we report on the observation of fluctuations in the luminescence spectrum on the scale of a few nm as expected for such localization effects. Our approach is based on scanning tunneling luminescence (STL) microscopy [16] which allows luminescence measurements under local carrier injection with a nm scale resolution. In order to reach the required spatial resolution, we used p-type single InGaN/GaN QW structures with a thin top GaN layer separating the QW from the injecting tip of the scanning tunneling microscope (STM) and we analyzed the spatial variations in the luminescence sp...

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Evidence of nanoscale Anderson localization induced by intrinsic compositional disorder in InGaN/GaN quantum wells by scanning tunneling luminescence spectroscopy

et al. 2018

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“…[9] Another near-field technique based on scanning tunneling electroluminescence (STL) microscopy [10][11][12][13][14] was used to identify the origin of PL broadening in nitride materials. [15][16][17] However, experiments were performed on inappropriate heterostructures with multiple QWs or a single QW too far from the surface which led to degraded spatial resolution, allowing only for emission fluctuations at large spatial scales to be observed. More recently, STL has nonetheless shown its capability to assess smaller-scale sources of PL broadening.…”

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confidence: 99%

Probing Local Emission Properties in InGaN/GaN Quantum Wells by Scanning Tunneling Luminescence Microscopy

Sauty

Alyabyeva

Lynsky

et al. 2022

Physica Status Solidi (b)

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Scanning tunneling electroluminescence (STL) microscopy is performed on a 3 nm‐thick InGaN/GaN quantum well (QW) with [In] = 0.23 such that the main light emission occurs in the green. The technique is used to map the radiative recombination properties at a scale of a few nanometers and correlate the local electroluminescence map with the surface topography simultaneously imaged by scanning tunneling microscopy. While the expected green emission is observed all over the sample, measurements performed on a 500 nm × 500 nm area around a 150 nm‐large and 2.5 nm‐deep hexagonal defect reveal intense emission peaks at higher energies close to the defect edges, features which are not visible in the macrophotoluminescence spectrum of the sample. Via a fitting of the local tunneling electroluminescence spectra, quantitative information on the fluctuations of the intensity, peak energy, width, and phonon replica intensity of the different spectral contributions is obtained, which provides information on carrier localization in the QW. This procedure also indicates that the carrier diffusion length on the probed area of the QW is shorter than 50 nm.

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Scanning Tunneling Luminescence Studies of Nitride Semiconductor Thin Films under Ambient Conditions

Cited by 2 publications

References 10 publications

Evidence of nanoscale Anderson localization induced by intrinsic compositional disorder in InGaN/GaN quantum wells by scanning tunneling luminescence spectroscopy

Evidence of nanoscale Anderson localization induced by intrinsic compositional disorder in InGaN/GaN quantum wells by scanning tunneling luminescence spectroscopy

Probing Local Emission Properties in InGaN/GaN Quantum Wells by Scanning Tunneling Luminescence Microscopy

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