Dielectric Function and Interband Transitions in Hg_1-xZn_xTe Solid Solutions

Abstract

The dielectric function sr + is, in Hgi_~Zn~Te is found, for the first time, at 293 K. It is deduced from spectroscopic ellipsometry measurements for the entire composition range and for photon energies ranging from 0.75 eV to 5.7 eV. A detailed analysis of the chemical treatments leading to the best surfaces which correspond to the highest values of s, at the E2 peak is presented. The oxydation of the surface after the last stripping is also studied. The pseudodielectric function is analysed for the critical point model. The variation, with x of the parameters describing the main critical transitions ED, ED + ho, El, El + hi and E2 are obtained. The results are discussed in relation to the band structure and to the properties of these compounds. RAsumA. La fonction didlectrique sr+ is, des solutions solides Hgi_~Zn~Te est donn6e, pour la premiAre fois, I 293 K. Ces r6sultats sent d6duits de mesures d'ellipsom6trie spectroscopique dans tout le domaine de composition et pour des 6nergies de photon allant de 0,75 eV I 5,7 eV. Les traitements chimiques permettant d'obtenir les meilleures surfaces correspondant aux plus fortes valeurs de s, au pic E2 sont analys6s en d6tail. De mime, l'oxydation de la surface est suivie par ellipsom6trie. La fonction pseudodidlectrique est analysde avec le modAle de points critiques. Les variations des paramAtres ddfinissant les principales transitions ED, ED + ho, El, El + hi et E2 sont donndes en fonction de la composition x. Ces rdsultats sont discutds en relation avec la structure de bande et les propridtds de ces solutions solides. 1.surfaces [3]. The fundamental gap Eo, at 0 K, varies strongly from -0.3 eV for HgTe to 2.4 eV for ZnTe with a high bowing parameter of at least 0.6 eV [4,5]. This bowing originates from

The dielectric function and interband transitions in

“…This behaviour is like those found for a great number of ternary compounds. It is different from those found for HgCdTe [27] where the deviation from linearity is at its maximum for x 0.8 and for HgZnTe where the maximum is near x 0.55 [33]. The asymmetry in the variations of E 1 and E 1 + 1 must be due therefore to Hg atomic levels and not to the bimodal distribution of near neighbours in HgZnTe and HgCdTe.…”

“…figure 6), do not present a significant bowing. This behaviour is found for 0 for HgZnTe [33] and probably for HgCdTe; on the other hand 1 has a quadratic variation with composition in a great number of III-V and II-VI alloys [27,44].…”

“…For Zn-rich samples the surface degrades too quickly during the time of 20 minutes necessary to monitor and ψ between 1.5 eV and 5.7 eV in steps of 10 meV. To overcome this difficulty, the ellipsometric data are monitored during wavelength scans which are sequentially repeated 10 to 15 times during the surface degradation [33]. The first wavelength scan is started at the photon energy E 2 when the last rinsing gives the highest value of ε i (E 2 ).…”

Optical Properties

“…The absorption coefficients a(E) in the fundamental absorption edge of Zn x Hg 1Àx Te have also been measured by several authors [264][265][266]. SE has been carried out on Zn x Hg 1Àx Te in the range between 0.75 and 5.7 eV by Castaing et al [267].…”

Electrical characterization of the p-Hg1−xZnxTe interface after anodic sulfidization treatments

“…The composition x of the samples was measured with an electronic microprobe and was found to be in the range of 0.19-a͒ Electronic mail: Daniel.Lemoine@insa-rennes.fr 0.23, which corresponds to a gap increase from 230 to 330 meV at 77 K. 12 The samples investigated are bulk slices whose surface is mechanically polished with alumina ͑grain sizes of 0.3, 0.04, and 0.02 m, respectively͒. Some of them are then submitted to a two-zone annealing treatment ͑wafer temperature of 400°C, Hg temperature of 380°C͒ in a closed silica ampoule in order to remove tellurium precipitates and to reduce the Hg vacancy concentration.…”