Defect-related density of states in low-band gap InxGa1−xAs/InAsyP1−y double heterostructures grown on InP substrates

Gfroerer, T. H.; Priestley, L. P.; Weindruch, F. E.; Wanlass, M. W.

doi:10.1063/1.1487449

Cited by 14 publications

(19 citation statements)

References 8 publications

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“…3,4 In this analysis it is important to note that, while PL spectroscopy is a very sensitive probe of radiative levels, the technique cannot detect states that couple weakly with light. On the other hand, our SBG PL measurements do not reveal the increasing density of shallow states that were also predicted by that model.…”

Section: Discussionmentioning

confidence: 99%

“…Historically, these structures were likely to contain a high density of defects, which produce new energy levels in the forbidden gap of the semiconductor. 2 However, we have also found evidence that the defect states themselves change with mismatch, 3 and these changes may contribute to the highly desirable outcomes noted above. Yet previous experiments on the InGaAs-based heterostructures described in this report reveal a special feature of lattice mismatch in this material system.…”

Section: Introductionmentioning

confidence: 93%

“…3 A simple defect recombination model assuming defect levels concentrated near the middle of the band gap fits well in the LM case but the model does not fit the experimental results for the mismatched structures. 3 A simple defect recombination model assuming defect levels concentrated near the middle of the band gap fits well in the LM case but the model does not fit the experimental results for the mismatched structures.…”

Section: Introductionmentioning

confidence: 93%

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Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates

Gfroerer

Gillespie

Campbell

et al. 2005

Journal of Applied Physics

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We are investigating a series of lattice-matched InxGa1−xAs∕InAsyP1−y double heterostructures with indium concentrations ranging between x=0.53 and x=0.78. The double heterostructures incorporating indium-rich alloys (x>0.53) experience lattice mismatch relative to the InP substrate. Previous work has produced convincing but indirect evidence that the distribution of defect levels in the InxGa1−xAs changes dramatically when the epistructure deviates from the lattice-matched condition. In particular, deep midgap states appear to give way to shallower near-band-edge states with increasing mismatch. Here, we report sub-band-gap photoluminescence measurements that explore these changes directly. We observe a broad low-energy peak in the spectra of the lattice-matched and nearly lattice-matched epistructures that is not present in the more mismatched case. The sub-band-gap emission blueshifts and grows superlinearly with photoexcitation up to and exceeding 1000W∕cm2. This unusual behavior is attributed to transitions between ordinary acceptor levels and deep, defect-related donorlike states. We find no evidence for the shallower defect states that we expected to arise with increasing lattice mismatch.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 93%

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Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates

Gfroerer

Gillespie

Campbell

et al. 2005

Journal of Applied Physics

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“…6 It has already been reported that DOS affects band structure of a compound and hence its bandgap also varied. [35][36][37] Furthermore, differences in the DOSs of AlN and GaN are responsible for making AlN as a wider bandgap material than GaN. When some of the Al atoms are replaced by Ga atoms in the AlN crystal, then the mixing of Al and Ga in the compound is responsible for the change in the DOS.…”

Section: Resultsmentioning

confidence: 99%

Ab initio study of the bandgap engineering of Al1−xGaxN for optoelectronic applications

Amin¹,

Ahmad²,

Maqbool³

et al. 2011

Journal of Applied Physics

172

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A theoretical study of Al 1−x Ga x N, based on the full-potential linearized augmented plane wave method, is used to investigate the variations in the bandgap, optical properties, and nonlinear behavior of the compound with the change in the Ga concentration. It is found that the bandgap decreases with the increase in Ga. A maximum value of 5.50 eV is determined for the bandgap of pure AlN, which reaches a minimum value of 3.0 eV when Al is completely replaced by Ga. The static index of refraction and dielectric constant decreases with the increase in the bandgap of the material, assigning a high index of refraction to pure GaN when compared to pure AlN. The refractive index drops below 1 for higher energy photons, larger than 14 eV. The group velocity of these photons is larger than the vacuum velocity of light. This astonishing result shows that at higher energies the optical properties of the material shifts from linear to nonlinear. Furthermore, frequency dependent reflectivity and absorption coefficients show that peak values of the absorption coefficient and reflectivity shift toward lower energy in the ultraviolet ͑UV͒ spectrum with the increase in Ga concentration. This comprehensive theoretical study of the optoelectronic properties predicts that the material can be effectively used in the optical devices working in the visible and UV spectrum.

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“…[3] We measure the radiative efficiency as a function of excitation power at 77K to study the changeover between defect-related (nonradiative) and radiative recombination in the structures. Since Auger recombination is negligible at low temperatures and defect recombination saturates at high carrier densities, we can usually obtain 100% internal quantum efficiency in our samples at 77K when the excitation rate is sufficiently high.…”

Section: Radiative Efficiencymentioning

confidence: 99%

Recombination in Low-Bandgap InGaAs

Gfroerer

Wanlass

2006

2006 IEEE 4th World Conference on Photovoltaic Energy Conference

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We review our investigation of recombination in InxGa1-xAs with indium concentrations ranging between x = 0.53 (i.e., lattice-matched to InP) and x = 0.78. External radiative efficiency measurements were used to study how defect-related and Auger mechanisms compete with radiative recombination. The results indicated that deep mid-gap levels facilitate defect-related recombination in lattice-matched InGaAs while shallower levels play a more important role in the indium-rich alloys. Subsequent subbandgap photoluminescence measurements confirmed the presence of deep levels in the lattice-matched InGaAs. The superlinear excitation dependence of the sub-gap emission led to a defect-related deep-donor/shallowacceptor pair model. Recent cathodoluminescence measurements of the subgap transitions show no spatial contrast, supporting the assignment of this mechanism to evenly distributed point defects. We hypothesize that the deep states observed in lattice-matched InGaAs are related to imperfections in the incorporation of indium or gallium, which become less likely as the indium concentration is increased.

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Defect-related density of states in low-band gap InxGa1−xAs/InAsyP1−y double heterostructures grown on InP substrates

Cited by 14 publications

References 8 publications

Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates

Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates

Ab initio study of the bandgap engineering of Al1−xGaxN for optoelectronic applications

Recombination in Low-Bandgap InGaAs

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