Effects of the host conduction band energy on the electronic band structure of ZnCdTeO dilute oxide alloys

Abstract

Interband optical transitions in highly mismatched ZnTe1−xOx and Zn1−yCdyTe1−xOx alloys with Cd content y = 0.1 and 0.32 and oxygen content x < 0.016 grown on ZnTe substrates were studied by photoreflectance (PR) and photoluminescence (PL) in a broad temperature range. The incorporation of oxygen into a Zn(Cd)Te matrix results in a splitting of the conduction band (CB) into two E− and E+ subbands forming a semiconductor with an intermediate band. In ZnTeO, only the E− band could be probed by PR and there was no PL signal. An addition of Cd atoms to form a ZnCdTeO quaternary alloy significantly improves the optical quality as evidenced by an emergence of an E+ related transition in the PR spectra and the appearance of a PL emission related to the E− band visible up to 260 K. Moreover, for Cd content above 25%, a change in the E− band character is observed from localized O-like to CB-like. The analysis of a PR signal shows a strong reduction of the temperature dependence of the energy gap of Zn(Cd)TeO alloys compared to ZnTe. The temperature related reduction of the bandgap shift with increasing O content is well explained by the band anticrossing interaction between the temperature dependent conduction band of the host Zn(Cd)Te matrix and the temperature independent energy of highly localized O states.

Mn impurity band and the effects of Mn position in III–V lattice: Pivotal contributions of Władek Walukiewicz to the understanding of ferromagnetism in semiconductors

“…One should note here that in the case of resonant configurations (i.e., when, in the absence of interactions, the energy of the localized impurity level coincides with the conduction or the valence band), the anticrossing model so far has only been applied to iso-electronic highly mismatched alloys, such as the dilute III-V and II-VI ternaries (Ga,As)N (Wu et al, 2002), ZnSe(O) (Mayer et al, 2012), CdTe(O) (Wełna et al, 2015), GaAs (Bi) (Alberi et al, 2007b), GaAs(Sb) (Alberi and Scarpulla, 2008), Ge(Sn) (Alberi and Scarpulla, 2008), as well as to some quaternary combinations, e.g., (Zn,Mn)(Te,O) (Yu et al, 2003) and (Zn,Cd)(Te,O) (Wełna et al, 2019). The (III,Mn)V FMS systems being discussed in this paper (where group-III ions are replaced by divalent Mn 2+ impurity) involve non-isoelectronic combinations of elements so that-in addition to new insights which studies of this configuration may provide in the area magnetic properties-they may also be valuable for a wider understanding of the physics of band anticrossing generally.…”

Absorption spectrum of doped highly mismatched alloys

“…Zn 1−y Cd y Te 1−x O x is a II-VI quaternary HMA in which ZnCdTe forms the standard semiconductor and oxygen plays the role of mismatching element. It has been the subject of extensive studies and used as an HMA of choice in making devices [8,15,20,[22][23][24][25][26]. We choose ZnCdTeO for our case study because there have been successful attempts in doping the E − band with chlorine donors [15].…”