Huge operation by energy gap of novel narrow band gap Tl sub(1-x) In sub(1-x) B sub(x) Se sub(2)(B = Si, Ge): DFT, x-ray emission and photoconductivity studies

• Published in: Materials research express 2016-02, Vol.3 (2), p.025902-025902
• Main Authors: Piasecki, M, Myronchuk, G L, Zamurueva, O V, Khyzhun, O Y, Parasyuk, O V, Fedorchuk, A O, Albassam, A, El-Naggar, A M, Kityk, I V
• Format: Article
• Language: English
• Subjects: Crystals; Energy distribution; Energy gap; Selenium; Semiconductors; Single crystals; Spectra; X rays
• ISSN: 2053-1591; 2053-1591
• DOI: 10.1088/2053-1591/3/2/025902

It is shown that narrow band gap semiconductors Tl sub(1-x) In sub(1-x) Ge sub(x) Se sub(2) are able effectively to vary the values of the energy gap. DFT simulations of the principal bands during the cationic substitutions is done. Changes of carrier transport features is explored. Relation with the changes of the near the surface states is explored . Comparison on a common energy scale of the x-ray emission Se K[beta] sub(2) bands, representing energy distribution of the Se 4p states, indicates that these states contribute preliminary to the top of the valence band. The temperature dependence of electrical conductivity and spectral dependence photoconductivity for the Tl sub(1-x) In sub(1-x) Ge sub(x) Se sub(2) and Tl sub(1-x) In sub(1-x) Si sub(x) Se sub(2) single crystals were explored and compared with previously reported Tl sub(1-x) In sub(1-x) Sn sub(x) Se sub(2). Based on our investigations, a model of centre re-charging is proposed. Contrary to other investigated crystals in Tl sub(1-x) In sub(1-x) Ge sub(x) Se sub(2) single crystals for x= 0.1 we observe extraordinarily enormous photoresponse, which exceed more than nine times the dark current. X-ray photoelectron core-level and valence-band spectra for pristine and Ar super(+)-ion irradiated surfaces of Tl sub(1-x) In sub(1-x) Ge sub(x) Se sub(2)(x= 0.1 and 0.2) single crystals have been studied. These results indicate that the relatively low hygroscopicity of the studied single crystals is typical for the Tl sub(1-x) In sub(1-x) Ge sub(x) Se sub(2) crystals, a property that is very important for handling these quaternary selenides as infrared materials operating at ambient conditions.