Bowing of the defect formation energy in semiconductor alloys

Ma, Jie; Wei, Su‐Huai

doi:10.1103/physrevb.87.241201

Cited by 25 publications

(24 citation statements)

References 28 publications

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“…25,26 The lack of a plasmon resonance indicates a significantly smaller free carrier density compared to phosphorus-doped Si NCs. This difference in phosphorus and boron incorporation efficiency has been shown by various computational models, [27][28][29] in which the lower active boron concentration in Si NCs was attributed to the larger formation energy of boron compared to phosphorus in Si NCs. Accordingly, the boron atoms prefer to reside on or near the surface of the Si NC where they do not affect the free carrier concentration.…”

Section: Resultsmentioning

confidence: 86%

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

2015

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Degenerately doped silicon nanocrystals are appealing plasmonic materials due to silicon's low cost and low toxicity. While surface plasmonic resonances of boron-doped and phosphorus-doped silicon nanocrystals were recently observed, there currently is poor understanding of the effect of surface conditions on their plasmonic behavior. Here, we demonstrate that phosphorus-doped silicon nanocrystals exhibit a plasmon resonance immediately after their synthesis but may lose their plasmonic response with oxidation. In contrast, boron-doped nanocrystals initially do not exhibit plasmonic response but become plasmonically active through postsynthesis oxidation or annealing. We interpret these results in terms of substitutional doping being the dominant doping mechanism for phosphorus-doped silicon nanocrystals, with oxidation-induced defects trapping free electrons. The behavior of boron-doped silicon nanocrystals is more consistent with a strong contribution of surface doping. Importantly, boron-doped silicon nanocrystals exhibit air-stable plasmonic behavior over periods of more than a year.

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Section: Resultsmentioning

confidence: 86%

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

2015

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“…Consequently, a Cu’ Cd defect in CdTe puts a strain on the lattice. A change in the lattice constant of the host lattice, as is shown here for CdTe 1-x Se x , can therefore reduce the strain that is induced by such a dopant, and can have an impact on the formation energy of the dopant defect, which in turn influences the solubility of the dopant [11]. …”

Section: Resultsmentioning

confidence: 99%

“…With Se having the same number of valence electrons as Te, substitution of the two does not introduce dopant-like acceptor or donor defects, but it can influence the behaviour of dopants such as Cu. The formation energy of dopants can be changed in the ternary or quaternary alloy compared to the pure binary compound due to electronic and strain effects: For the CdTe 1-x S x system Ma and Wei predicted a bowing in the formation energy of the Cu’ Cd defect, which causes an increased solubility of the defect in the alloy compared to the pure binary constituents [11]. Other effects of alloying are changes in the lattice constant, in the band gap, in the band alignment and in the solubility of dopants.…”

Section: Introductionmentioning

confidence: 99%

Structural and electronic properties of CdTe_1-xSe_x films and their application in solar cells

Lingg

Spescha

Haass

et al. 2018

Science and Technology of Advanced Materials

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The performance improvement of conventional CdTe solar cells is mainly limited by doping concentration and minority carrier life time. Alloying CdTe with an isovalent element changes its properties, for example its band gap and behaviour of dopants, which has a significant impact on its performance as a solar cell absorber. In this work, the structural, optical, and electronic properties of CdTe1-xSex films are examined for different Se concentrations. The band gap of this compound changes with composition with a minimum of 1.40 eV for x = 0.3. We show that with increasing x, the lattice constant of CdTe1-xSex decreases, which can influence the solubility of dopants. We find that alloying CdTe with Se changes the effect of Cu doping on the p-type conductivity in CdTe1-xSex, reducing the achievable charge carrier concentration with increasing x. Using a front surface CdTe1-xSex layer, compositional, structural and electronic grading is introduced to solar cells. The efficiency is increased, mostly due to an increase in the short-circuit current density caused by a combination of lower band gap and a better interface between the absorber and window layer, despite a loss in the open-circuit voltage caused by the lower band gap and reduced charge carrier concentration.

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“…Other studies suggested different DX configurations of Si in Al x Ga 1-x As to be related to different numbers of Al atoms surrounding the isolated Si donor [40][41][42]. In addition, the negative charge state of a DX center and the positively charged donor were theoretically suggested to form a complex (denoted DDX) at high doping concentration via Coulomb interaction [43]. In that case, the DDX center is more stable than the single DX center and its formation increases further self-compensation effect.…”

Section: Concepts Of the Negative-u And DX Centersmentioning

confidence: 99%

Electron Paramagnetic Resonance Studies of Point Defects in AlGaN and SiC

Trinh¹

2015

Linköping Studies in Science and Technology. Dissertations

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Point defects in semiconductor materials are known to have important influence on the performance of electronic devices. For defect control, knowledge on the model of defects and their properties is required. Information on defects, such as the symmetry and the localization of spins, is essential for identification of defects and understanding their electronic structure. Such information can be obtained from Electron Paramagnetic Resonance (EPR). In many cases, the energy levels of defects can be determined from photoexcitation EPR (photo-EPR) or temperature dependence of the EPR signal. The thesis contains six papers, focusing on the identification and electronic structure investigation of defects and impurities in Al x Ga 1-x N (x~0.7-1) and silicon carbide (SiC) using EPR in combination with other electrical characterizations and density functional theory calculations.The two first papers concern EPR studies of silicon (Si) in AlGaN alloys. Due to its direct and wide band gap which can be tailored from 3.4 eV for GaN to 6.2 eV for AlN, high-Al-content wurtzite Al x Ga 1-x N (x≥0.7) has been considered as a promising material for fabrication of compact, highefficiency and non-toxic deep ultraviolet light-emitting diodes (LEDs) and laser diodes (LDs) for replacing low-efficiency and toxic mercury lamps in water/air purification and sterilization. Si is commonly used for n-type doping in AlGaN and AlN, but the conductivity of Si-doped Al x Ga 1-x N was often reported to drop abruptly at high Al content (x>0.7) and the reason was often speculated to be due to either carrier compensation by other deep levels or Si itself when it transforms from a shallow donor to a DX (or negative-U) center which acts as an acceptor. In paper 1, we showed that Si already forms a stable DX center in Al x Ga 1-x N with x ~0.77. However, with the Fermi level locating only ~3 meV below the neutral charge state, E d , Si still behaves as a shallow donor. Negligible carrier compensation by oxygen (O) in Al 0.77 Ga 0.23 N:Si layers was observed, suggesting that at such Al content, O does not seem to hinder the n-type doping in the material. In paper 2, we found the coexistence of two Si DX centers, the stable DX1 and the metastable DX2, in Al x Ga 1-x N for x≥0.84. For the stable DX1 center, abrupt deepening of the energy level of the negative charge state DX -, E DX , which determines the ionization energy E a of the Si donor, with increasing of the Al content for x≥0.83 was observed. The dependence of E a on the Al content in Al x Ga 1-x N:Si layers (0.79≤x≤1) was determined. The results explain the drastic decrease of the conductivity as often reported for Al x Ga 1-x N:Si in previous transport studies. For the metastable DX2 center, we found that the E DX level remains close to E d for x=0.84÷1.SiC is a wide band-gap semiconductor having high-thermal conductivity, high breakdown field, and large saturated electron drift velocity which are iv essential properties for high-voltage and high-power devices. In paper 3, the identif...

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Bowing of the defect formation energy in semiconductor alloys

Cited by 25 publications

References 28 publications

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

Structural and electronic properties of CdTe_1-xSe_x films and their application in solar cells

Electron Paramagnetic Resonance Studies of Point Defects in AlGaN and SiC

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Bowing of the defect formation energy in semiconductor alloys

Cited by 25 publications

References 28 publications

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

Structural and electronic properties of CdTe1-xSex films and their application in solar cells

Electron Paramagnetic Resonance Studies of Point Defects in AlGaN and SiC

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Product

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Structural and electronic properties of CdTe_1-xSe_x films and their application in solar cells