Ukrainian Journal of Physical Optics 

Volume 22, Issue 2, 2021

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Electronic band structure of cubic solid-state CdTe1–xSex solutions

1Ilchuk H.A., 2Andriyevsky B., 3Kushnir O.S., 1*Kashuba A.I., 1Semkiv I.V. and 1Petrus R.Yu.

1Department of General Physics, Lviv Polytechnic National University, 12 Bandera   Street, 79046 Lviv, Ukraine. *
2Faculty of Electronics and Computer Sciences, Koszalin University of Technology,   2 Sniadeckich Street, 75-453 Koszalin, Poland
3Electronics and Computer Technologies Department, Ivan Franko National   University of Lviv, 107 Tarnavsky Street, 79005 Lviv, Ukraine 

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Abstract. We report on the electronic band structure of solid-state solutions CdTe1–xSex (CTS, 0 < x ≤ 5/16) calculated in the framework of density functional theory. The structure of CTS is calculated following from the ‘parent’ binary compound CdTe, which is crystallized in a cubic phase. The bandgap of CTS is found to be of a direct type for all of the solid-state solutions under test. A decrease in the bandgap Eg is found with increasing selenium content x. The Eg(x) dependence reveals some deviations from a simple linear function. The free-carrier concentration increases with increasing selenium content. It is shown that interaction among the atoms of host matrix (CdTe) and substitution selenium atoms causes splitting of the valence bands into heavy-hole and light-hole subbands and spin-orbit splitting, while the conduction bands remain unaffected. The dependence of refractive index on the selenium content is obtained

Keywords: solid-state solutions, CdTe, concentration dependences, electronic band structure, carrier concentration, refractive index

UDC: 544.225.22, 621.315.592, 535.323
Ukr. J. Phys. Opt. 22 101-109
doi: 10.3116/16091833/22/2/101/2021
Received: 22.02.2021

Анотація. У рамках теорії функціонала густини розраховано електронну зонну структуру твердотільних розчинів CdTe1–xSex (CTS, 0 < x ≤ 5/16). Структуру CTS одержано, виходячи з «материнської» бінарної сполуки CdTe, яка кристалізується в кубічній фазі. Встановлено, що всі вивчені нами твердотільні розчини CTS є прямозонними. Виявлено звуження ширини щілини Eg зі зростанням вмісту селену x. Залежність Eg(x) дещо відхиляється від лінійної. Концентрація вільних носіїв зростає зі зростанням вмісту селену. Показано, що взаємодія між атомами матриці-господаря (CdTe) та атомами заміщення селену викликає розщеплення валентних смуг на важкі діркові та легкі діркові підзони, а також спін-орбітальне розщеплення, тоді як смуги провідності залишаються незмінними. Одержано залежність показника заломлення від вмісту селену.

Ключові слова: тверді розчини, CdTe, концентраційні залежності, електронна зонна структура, концентрація носіїв, показник заломлення

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