Urbach Tail and Optical Absorption in Layered Semiconductor TlGaSe2(1-x)S2xSingle Crystals

Duman, S.; Gürbulak, B.

doi:10.1238/physica.regular.072a00079

Cited by 19 publications

(10 citation statements)

References 34 publications

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“…Finally, the Debye temperatures estimated from the appropriate dependences for TlGaSe 2 and TlGaSe 2 :Zn are 203 and 217±2 K, which agrees well with the data of Ref. [16]. Eq.…”

Section: Resultssupporting

confidence: 89%

“…The coexistence of these transitions in the A III B III C 2 VI crystals has earlier been reported in Refs. [1,16,17,36,37]. We have obtained the Table 2 for the temperatures 100, 150, 200, 250 and 300 K. It is known that the doping leads to decrease in both the direct and indirect bandgaps, when compared to the pure TlGaSe 2 crystals [16].…”

Section: +mentioning

confidence: 99%

“…Apart from the direct and indirect transmission bands and the temperature points of phase transitions, the previous investigations on the subject have also been concerned with the phonon energy, the temperature coefficient and the so-called 'steepness' parameter of the Urbach energy, as well as the Debye parameter of A III B III C 2 VI single crystals [4,[16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

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Study of optical absorption in TlGaSe2:Zn2+ single crystals

Makhnovets¹,

Myronchuk²,

Піскач³

et al. 2018

Ukr. J. Phys. Opt.

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Abstract. We report the results of experimental studies for the optical absorption in TlGaSe 2 :Zn 2+ single crystals grown using a modified Bridgman-Stockbarger technique. The absorption measurements at different temperatures are performed with the steps 50 K. The analysis of the experimental data yield in the absorption coefficients of TlGaSe 2 :Zn varying from 20 to 800 cm -1 in the temperature region 100-300 K. Direct and indirect bandgap values for TlGaSe 2 :Zn 2+ are calculated as functions of temperature. These values are respectively equal to 2.22 and 2.04 eV at 100 K. It is revealed that the spectral dependences of the absorption coefficient in the region 60-130 cm -1 follow the Urbach rule, whereas the corresponding steepness parameter and the Urbach energy increase with increasing temperature.

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“…Finally, the Debye temperatures estimated from the appropriate dependences for TlGaSe 2 and TlGaSe 2 :Zn are 203 and 217±2 K, which agrees well with the data of Ref. [16]. Eq.…”

Section: Resultssupporting

confidence: 89%

Section: +mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of optical absorption in TlGaSe2:Zn2+ single crystals

Makhnovets¹,

Myronchuk²,

Піскач³

et al. 2018

Ukr. J. Phys. Opt.

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“…The determined energy band gaps E gi = 2.45 eV and E gd = 2.63 eV (TlGaS 2 ), E gi = 1.97 eV and E gd = 2.26 eV (TlGaSe 2 ), and E gi = 2.27 eV and E gd = 2.47 eV (TlInS 2 ) agree well with the corresponding data reported earlier [25,26]. It is observed in Fig.…”

Section: Resultssupporting

confidence: 91%

Composition dependence of lattice parameters and band gap energies of thallium based layered mixed crystals

Gasanly

2014

Indian J Phys

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Compositional dependence of lattice parameters and unit cell volumes of TlMeX 2 -type (Me = Ga or In and X = S or Se) layered mixed crystals with monoclinic structure has been studied by X-ray diffraction technique. It is revealed that the lattice parameters of TlGa 1-x In x Se 2 , TlGa(S 1-x Se x ) 2 , TlGa 1-x In x S 2 and TlIn(Se 1-x S x ) 2 mixed crystals increase due to the substitution of gallium atoms by indium and sulfur atoms by selenium. Moreover, the absorption edges of these mixed crystals have been investigated through the transmission and reflection measurements in the wavelength range of 400-1,100 nm. The analysis of absorption data has revealed the presence of both optical indirect and direct transitions. It is found that the energy band gaps of mixed crystals decrease due to the substitution of gallium atoms by indium and of sulfur atoms by selenium.

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“…Studies of the optical absorption spectra near the interband absorption edge are widely used for characterization of semiconductor materials. [1][2][3] The spectral dependence at low-energy absorption edge is well approximated by the Urbach exponential decay. 4 However, the interband absorption usually overlaps with residual absorption by free carriers, masking the true dependence of the absorption tail.…”

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confidence: 98%

Urbach tail studies by luminescence filtering in moderately doped bulk InP

Subashiev

Semyonov

Chen

et al. 2010

Applied Physics Letters

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The shape of the photoluminescence line registered from a side edge of InP wafer is studied as function of the distance from the excitation spot. The observed red shift in the luminescence maximum is well described by radiation filtering and is consistent with the absorption spectra. Our method provides an independent and accurate determination of the Urbach tails in moderately doped semiconductors.Studies of the optical absorption spectra near the interband absorption edge are widely used for characterization of semiconductor materials. [1][2][3] The spectral dependence at low-energy absorption edge is well approximated by the Urbach exponential decay. 4 However, the interband absorption usually overlaps with residual absorption by free carriers, masking the true dependence of the absorption tail. In doped samples, the absorption tail is additionally broadened and this effect is also masked by the residual electronic absorption.Available theories 5-8 do not provide description of the interband absorption tailing in the entire energy range from interband to deep tails. Still, they give an insight on the nature of the bandgap fluctuations causing the tailing. Tailing with Gaussian-like asymptotics is characteristic of classical potential fluctuations, 5 whereas exponential decrease with square-root energy dependence in the exponent is indicative of quantum effects in the band tailing. 6,7 Temperature variations of the tailing are accounted for by the adiabatic potential of thermally excited phonons. 8 In a limited experimental range near the fundamental edge the observed absorption spectra may not differ noticeably from the Urbach law, 7 but the temperature and the concentration dependence of the tailing parameters can be very informative. Therefore, accurate studies of the tailing dependence are highly desirable.In this letter we describe an alternative experimental method for studying the semiconductor absorption edge by measuring the red shift of the peak of the luminescence line, registered from the side edge of the wafer. This shift is sensitive to the sample transparency at the peak wavelength, which is in the region where residual absorption dominates. We show that for moderately doped n-InP wafers this technique provides an accurate determination of the Urbach tailing energy.We used 350 µm-thick InP wafers, doped n-type (S) in the range n = 2 × 10 17 to 6 × 10 18 cm −3 and measured the reflection and the transmission spectra to evaluate the absorption coefficient α. 9 For all moderately doped samples, n ≤ 2 × 10 18 cm −3 , in the temperature range 78 to 320 K, the absorption edge exhibits an Urbach-type energy dependence in the range α = 10 to 100 cm −1 . For lower doped samples, n < 10 18 cm −3 , the observed a) Electronic

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Urbach Tail and Optical Absorption in Layered Semiconductor TlGaSe_2(1-x)S_2xSingle Crystals

Cited by 19 publications

References 34 publications

Study of optical absorption in TlGaSe2:Zn2+ single crystals

Study of optical absorption in TlGaSe2:Zn2+ single crystals

Composition dependence of lattice parameters and band gap energies of thallium based layered mixed crystals

Urbach tail studies by luminescence filtering in moderately doped bulk InP

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