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Journal ArticleDOI

Effect of alloy disorder on photoluminescence in HgCdTe

01 Aug 2009-Physica Status Solidi B-basic Solid State Physics (WILEY‐VCH Verlag)-Vol. 246, Iss: 8, pp 1858-1861
TL;DR: In this paper, the peak energy was found to be less than that of the energy gap by a certain value δE that depended on temperature, attributed to recombination of excitons localized at composition non-homogeneities.
Abstract: Hg 1-x Cd x Te samples with x=0.38 and 0.57 fabricated by molecular beam epitaxy, both as-grown and after annealing, were studied. Photoluminescence (PL) was measured in the temperature range 4.2 < T< 300 K. The PL peak energy was found to be less than that of the energy gap by a certain value δE that depended on temperature. This effect was attributed to recombination of excitons localized at composition non-homogeneities. An analysis was carried out that provided a way for evaluation of a non-homogeneity measure. The amplitude of the non-homogeneities was shown to decrease by about 50% as a result of post-growth annealing in a He atmosphere and Hg vapour.
Citations
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Journal ArticleDOI
Abstract: Photoluminescence of HgCdTe epitaxial films and nanostructures and electroluminescence of InAs(Sb,P) light-emitting diode (LED) nanoheterostructures were studied. For HgCdTe-based structures, the presence of compositional fluctuations, which localized charge carriers, was established. A model, which described the effect of the fluctuations on the rate of the radiative recombination, the shape of luminescence spectra and the position of their peaks, was shown to describe experimental photoluminescence data quite reasonably. For InAs(Sb,P) LED nanoheterostructures, at low temperatures (4.2–100 K) stimulated emission was observed. This effect disappeared with the temperature increasing due to the resonant ‘switch-on’ of the Auger process involving transition of a hole to the spin-orbit-splitted band. Influence of other Auger processes on the emissive properties of the nanoheterostructures was also observed. Prospects of employing II–VI and III–V nanostructures in light-emitting devices operating in the mid-infrared part of the spectrum are discussed.

14 citations

Journal ArticleDOI
TL;DR: In this article, photoluminescence and temperature-dependent Hall measurements of nonintentionally doped HgCdTe epilayers were compared and it was shown that the acceptor energy levels of the mercury vacancy and its negative-U property correspond to a stabilization of the ionized state V− of the vacancy compared to its neutral state V0.
Abstract: Photoluminescence and temperature-dependent Hall measurements of nonintentionally doped HgCdTe epilayers were compared. These films were grown by liquid phase epitaxy and postannealed under different conditions as follows: a p-type annealing was used to control the mercury vacancy concentration and a n-type annealing under saturated Hg atmosphere was used to fill the mercury vacancies. The comparison of the photoluminescence measurements with Hall effect measurements allows us to identify the two acceptor energy levels of the mercury vacancy and to evidence its “negative-U” property corresponding to a stabilization of the ionized state V− of the mercury vacancy compared to its neutral state V0.

12 citations

Journal ArticleDOI
TL;DR: In this article, the relationship between photoluminescence and temperature-dependent Hall measurements was carried out on unintentionally doped HgCdTe epilayers with cadmium composition of 32.7%.
Abstract: Correlations between photoluminescence and temperature-dependent Hall measurements were carried out on unintentionally doped HgCdTe epilayers with cadmium composition of 32.7%. These films were grown by liquid-phase epitaxy and post-annealed under different conditions as follows: a p-type annealing was used to control the mercury vacancy concentration, and an n-type annealing under saturated mercury atmosphere was used to fill the mercury vacancies. Comparison of the results obtained by these two characterization techniques allowed us to identify the two acceptor energy levels of the mercury vacancy. Moreover, the “U-negativity” of the vacancy was evidenced: the ionized state V− is stabilized under the neutral state V0 by the dominance of the Jahn–Teller effect over Coulombic repulsion. Finally, three epilayers with different cadmium compositions were also characterized to complete this study.

8 citations

Book ChapterDOI
04 Sep 2010

1 citations

DOI
23 Jan 2013
TL;DR: In this article, it is suggested that observation of photoluminescence of the narrow-gap semiconductor at high temperatures can be explained by taking into account HgCdTe alloy disorder as is the case, for example, in structures based on III-nitrides.
Abstract: Prospects of fabrication of high-temperature (up to 300K) infrared emitters based on HgCdTe alloys is discussed on the basis of the results of the study of photoluminescence of hetero-epitaxial structures. The structures were grown by molecular-beam epitaxy and emitted light with wavelength of 1.5 to 4.3µm at room temperature. It is suggested that observation of photoluminescence of the narrow-gap semiconductor at high temperatures and the specific shape of photoluminescence spectra can be explained by taking into account HgCdTe alloy disorder as is the case, for example, in structures based on III-nitrides. Requirements for technology considerations for the optically-pumped high-temperature infrared emitters based on HgCdTe are discussed.

1 citations


Cites background from "Effect of alloy disorder on photolu..."

  • ...It has been shown by various authors that it was this effect that defined deviation of the energy of excitonic PL line from calculated Eg(T) dependence at low temperatures [5,6,8,14,15]....

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  • ...The latter value corresponds to the broadening caused by purely stochastic fluctuations of the alloy composition [14], and indicates high structural perfection of the LPE-grown films, yet PL signal from these films at T>150K was impossible to detect....

    [...]

References
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Journal ArticleDOI

103 citations

Journal ArticleDOI
TL;DR: In this paper, the temperature dependence of the fundamental absorption edge of a series of Hg1−xCdxTe alloys was investigated in the light of the three-dimensional theory of direct-allowed excitons, and precise values for the fundamental Γ8−Γ6 interband transition energy in a temperature range extending from 0 to 300 K were obtained.
Abstract: We have investigated the temperature dependence of the fundamental absorption edge of a series of Hg1−xCdxTe alloys (with composition x ranging from 0.5 to 1). Analyzing our data in the light of the three‐dimensional theory of direct‐allowed excitons, we find precise values for the fundamental Γ8‐Γ6 interband transition energy in a temperature range extending from 0 to 300 K. All experimental results, including previous data for HgTe and mercury‐rich Hg1−xCdxTe alloys, are well accounted for using a simple empirical formula: Eg (eV)=−0.303(1−x)+1.606x−0.132x(1−x)+[6.3(1−x) −3.25x −5.92x(1−x)]10−4T2/[11(1−x)+78.7x+T]. This expression, which is valid for all compositions 0≤x≤1 and temperatures 0≤T≤500 K, predicts an alloy composition such that the band‐gap energy is temperature independent: We find x=0.505. Finally, it can be used for technological application purpose (far‐infrared detection as well as optical‐fiber communications performed at realistic values of the temperature) and gives accurate values f...

99 citations

Journal ArticleDOI
TL;DR: In this article, the influence of lateral fluctuations of the fundamental band gap on the macroscopic light absorptance and emission spectra of spatially inhomogeneous semiconductors was investigated.
Abstract: This work investigates the influence of lateral fluctuations of the fundamental band gap on the macroscopic light absorptance and emission spectra of spatially inhomogeneous semiconductors. A model assuming a Gaussian distribution for the local band gaps yields closed-form expressions for the spectral absorptance and emission. Band gap fluctuations broaden the absorption edge of the fundamental band gap, as well as the associated emission peak. The spectral position of the photoluminescence emission peak depends on the length scale of the fluctuations in relation to the characteristic charge carrier transport length. We apply the model to experimental results from Cu(In1−x,Gax)Se2 thin films routinely used as photovoltaic absorbers in thin-film ZnO/CdS/Cu(In,Ga)Se2 heterojunction solar cells. The films feature band gap fluctuations with standard deviations between 15 and 65 meV which would lead to losses in the range of 5–80 mV for the open circuit voltage of solar cells made from these films. The pure ternary compounds CuInSe2 and CuGaSe2 exhibit smaller standard deviations than their quaternary alloys. This experimental finding indicates alloy disorder as one possible source of band gap inhomogeneities. The length scale of the observed fluctuations turns out to be much smaller than the minority carrier diffusion length. Hence, the band gap fluctuations occur on a length scale below 100 nm.

94 citations

Journal ArticleDOI
TL;DR: In this article, a systematic photoluminescence study of CdxHg1−xTe has been carried out versus solid composition to follow step by step the evolution of the optical radiative mechanisms involved.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the electrical properties of p-type, low-arsenic-doped Hg1−xCdxTe (x∼0.3, carrier concentration ∼1×10+15'cm−3) suitable for fabrication of high-operating-temperature photodetectors was carried out.
Abstract: A study of the electrical properties of p-type, low-arsenic-doped Hg1−xCdxTe (x∼0.3, carrier concentration ∼1×10+15 cm−3) suitable for fabrication of high-operating-temperature photodetectors was carried out. The arsenic-doped HgCdTe samples were prepared by molecular beam epitaxy using an elemental arsenic source and were characterized by Hall measurements at 77 K after the samples were subjected to four different arsenic activation annealing schemes with annealing temperatures ranging from 300 to 450 °C. For comparison purpose, a sample doped to low-10+16 cm−3 was also prepared and subjected to the same annealing schemes. Although the four annealing schemes had little influence on the Hall data of the 10+16 cm−3 sample, they had significant impact on the Hall data of the 10+15 cm−3 sample. Furthermore, it was found that the Hall data could not be explained by any scattering mechanisms but could be satisfactorily modeled by a two-layer model in which an n-type skin layer is included.

27 citations