Charge carrier transfer in amorphous (GeS)1-хBiх films

Abstract

The influence of Bi additions on the electrical and photoelectrical properties of amorphous (GeS) 1-х Bi х films (0 ≤ ≤ ≤ ≤ х ≤ ≤ ≤ ≤ 0.15) has been investigated. Adding Bi to amorphous GeS condensates leads to changes in the mechanism of conductivity and inversion of the conductivity type. Bi-additives reduce the activation energy of photoconductivity and photosensitivity of the GeS films. The changes of the physical properties of the films are explained considering a heterogeneous structure of the condensates and defect states in the mobility gap.

Ultrahigh drive current and large selectivity in GeS selector

“…The band gap of amorphous GeS can be determined to be 1.50 eV by linear fitting of the near absorption edge in the Tauc plot, (αhν) 1/2 as a function of photon energy hν displayed in Fig. 4a, where α is the absorption coefficient, which is consistent with the reported one 25 . A 0.116 eV energy of Urbach tail (E u ), known as the width of the localized band tail, can also be obtained by fitting the α versus hν.…”

“…Noticeably, the hybridization of S-based Ge alloy presents 15% larger than that of Te-based Ge alloy, enabling large ON current. Moreover, the sharp increase of band gap (GeTe 6 0.6 eV 24 , GeSe 1.0 eV 15 , GeS 1.5 eV 25 ) is beneficial for achieving low OFF current and therefore larger selectivity. As smaller covalent radius also leads to stronger bonds with Ge atom (bond energy: Te-Ge 192 kJ mol −1 , Se-Ge 234 kJ mol −1 , S-Ge, 266 kJ mol −1 ), and an increase of the crystallization temperature would be expected to minimize the undesired crystallization.…”

Chalcogenide Ovonic Threshold Switching Selector

“…As the most representative element in the chalcogen, the 16th element sulfur (S) has been the subject of numerous investigations, regarding its crystal structure [84][85][86][87][88][89], electronic structure [84,85,[90][91][92], thermodynamic properties [84], and other physical characteristics (Fig. 17a).…”

“…In 2020, Jia et al first reported S-based OTS materials [66], GeS, and then Ge-S alloys were systematically studied. Since the atomic radius of S atoms was just 0.88 Å, > 0.3 Å smaller than Se and Te atoms, the Ge-S compounds exhibited high crystallization temperatures, 380 °C for GeS and exceeding 600 °C for GeS 2 [92]. The mobility gap of Ge-S system increased with an elevated concentration of S, for S-rich Ge-S, the mobility gap ranged from 2.6 V to 3.4 eV and it could reach 3.8 eV in pure S (Fig.…”