Ab initioguided optimization of GaTe for radiation detection applications

Abstract

The development of semiconductor-based radiation detectors that display high energy resolution while operating at room temperature is a pressing need for both scientific applications as well as homeland security. Practice has proven that the real performance of materials in such applications is often hindered by intrinsic defects and accidental impurities. Experimental efforts to improve the properties of such materials are both time consuming and costly, since they rely largely on trial and error. In this paper, the properties of gallium telluride (GaTe)-a high Z, moderate band gap semiconductor-are investigated for room-temperature radiation detection applications. Systematic theoretical modeling based on density functional theory calculations is used to suggest experimental processes to grow this semiconductor with optimal properties, by judiciously identifying the most detrimental native defects and devising ways to minimize their occurrence as well as compensating their electronic impact on the crystal. The analysis suggests that material grown Ga-rich would have significantly higher resistivity, carrier mobilities, and carrier lifetimes compared to Te-rich material. In addition, Ge doping and In doping can be effective for carrier compensation of the material. Doping with Ge can be especially effective, if the ambipolar nature of substitutional incorporation on both Ga and Te sites is exploited.

Novel III-Te–graphene van der Waals heterojunctions for optoelectronic devices

“…[4][5][6] In addition to solar cells and thermoelectric devices, [7][8][9][10] GaTe has also been considered for detection of g and X-ray radiation. [11][12][13] This because with a high average atomic number and a crystal structure of relatively dense packing, GaTe has a high stopping power for very energetic photons. Moreover, its moderate band gap is optimal for radiation detection.…”

Bandgap Restructuring of the Layered Semiconductor Gallium Telluride in Air

“…We note that the PL and optical absorption spectra associated with as-cleaved GaTe reappear in samples upon removal of a surface layer via exfoliation. [13][14][15][16][17] Gallium telluride has a monoclinic structure (C2/m space group) with a metastable hexagonal phase. The peaks at 112, 117, 164, 177, 210, 270, and 283 cm −1 observed in the as-cleaved sample have been previously identifi ed for monoclinic GaTe.…”

Ionic current and polarization effect in TlBr

“…We use density functional theory 11 with the generalized gradient approximation for the exchange-correlation as developed by Perdew, Burke and Erzenhof (PBE). 12 We performed tests using more accurate HSE06 hybrid functional 13,14 in smaller cells and verified the accuracy of PBE for the analysis presented here 10 . The projector augmented-wave method, 15 as implemented in the VASP code, [16][17][18] is used to treat core electrons.…”

“…1,2 The high performance stems from the material's favorable properties, namely, a moderate band gap (2.7 eV), very long carrier drift length (lifetime up to 10 −4 s) , high room-temperature resistivity (around 10 11 Ω.cm −1 ) 3 and high average atomic number. 4 However, its widespread adoption for radiation detection applications-such as medical and space imaging or port monitoring for national securityhas been prevented due to invariable performance degradation after operation times that vary from hours to several weeks.…”

“…For TlBr (P m3m structure), the ions move in 100 directions on equivalent sites forming a simple cubic lattice, for which f = 0.655 and a 0 equals the lattice constant. The term containingñ excess vac,i accounts for the possibility of an extrinsic concentration of vacancies, which may form to keep charge neutrality in the presence of charged impurities, for example 10 . In order to theoretically estimate ionic current in TlBr, all quantities in Eqs.…”