Home

Search

Collections

Journals

About

Contact us

My IOPscience

Ab initio investigation of the structural and electronic properties of amorphous HgTe

This content has been downloaded from IOPscience. Please scroll down to see the full text. 2014 J. Phys.: Condens. Matter 26 045503 (http://iopscience.iop.org/0953-8984/26/4/045503) View the table of contents for this issue, or go to the journal homepage for more

Download details: IP Address: 130.60.206.43 This content was downloaded on 11/07/2014 at 14:05

Please note that terms and conditions apply.

Journal of Physics: Condensed Matter J. Phys.: Condens. Matter 26 (2014) 045503 (7pp)

doi:10.1088/0953-8984/26/4/045503

Ab initio investigation of the structural and electronic properties of amorphous HgTe Huxian Zhao1 , Xiaoshuang Chen1,3 , Jianping Lu2 , Haibo Shu1 and Wei Lu1 1

National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083, People’s Republic of China 2 Department of Physics and Astronomy, Curriculum in Applied and Materials Sciences, University of North Carolina, Chapel Hill, NC 27599, USA E-mail: [email protected] Received 15 July 2013, revised 23 October 2013 Accepted for publication 9 December 2013 Published 8 January 2014 Abstract

We present the structure and electronic properties of amorphous mercury telluride obtained from first-principle calculations. The initial configuration of amorphous mercury telluride is created by computation alchemy. According to different exchange–correlation functions in our calculations, we establish two 256-atom models. The topology of both models is analyzed in terms of radial and bond angle distributions. It is found that both the Te and the Hg atoms tend to be fourfold, but with a wrong bond rate of about 10%. The fraction of threefold and fivefold atoms also shows that there are a significant number of dangling and floating bonds in our models. The electronic properties are also obtained. It is indicated that there is a bandgap in amorphous HgTe, in contrast to the zero bandgap for crystalline HgTe. The structures of the band tail and defect states are also discussed. Keywords: HgCdTe, amorphous, DFT, electronic properties (Some figures may appear in colour only in the online journal)

1. Introduction

has been shown that HgTe has a great potential application in spintronics [8]. But the choice of substrate for epitaxial growth has limited the performance of HgTe devices. Although it can well match the lattice, the great expansion mismatch with the Si readout chip is the biggest problem facing the traditional substrate. Moreover, it is quite difficult and expensive to achieve large-scale devices on traditional substrates. A possible solution of the problem is a silicon-based device, which can satisfy the matching of thermal expansion of the Si readout chip. Also, silicon-based HgTe can greatly improve the reliability of interconnects with the readout chip. Thus, the use of Si substrates is very attractive in technology. Furthermore, the increase of size and the reduction of cost encourage the use of Si substrates. However, the great lattice mismatch between Si and HgTe, about 19%, is the biggest obstacle of the Si-based epitaxial technique [9]. In experiments, taking advantage of surface passivation technology [10], it has already proved possible

HgTe has attracted considerable attention because of its special properties [1] and important applications in the infrared field. Its alloy with CdTe is one of the most important infrared materials [2–4]. In addition, both theoretical and experimental results have recently revealed a unique state of matter, called a topological insulator, in HgTe quantum wells [5, 6]. In this phase, although the bulk is an insulator, the current is still carried by the electronic state of the surface. Under the protection of time-reversal symmetry, this kind of metallic state on the surface is very stable; it is only related to the topology of electronic states of the material, and cannot be affected by impurities or disorder. In addition, carriers in surface states are spin–momentum locked [7]. It 3 Address for correspondence: National Laboratory for Infrared Physics,

Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu-Tian Road, Shanghai 200083, People’s Republic of China. 0953-8984/14/045503+07$33.00

1

c 2014 IOP Publishing Ltd Printed in the UK

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

Table 1. The statistical distribution of the main structural components in the LDA and PW91 calculations.

Coordination

Model

Volume/Hg–Te ˚ 3 /Hg–Te) (A

Atom

2

3

4

5

6

n

X–X (%)

LDA

18.37

Te

0 —

22 17%

92 72%

13 10%

1 1%

3.95

10.30

Hg

2 2%

18 14%

90 70%

15 12%

3 2%

3.99

11.35

Te

0 —

34 26%

82 64%

11 9%

1 1%

3.84

10.18

Hg

1 1%

32 25%

80 63%

13 10%

2 1%

3.87

10.91

PW91

22.34

After the initial amorphous structure is formed, a melt-quench process from 3000 to 200 K and a full structural relaxation would be carried out based on density function theory (DFT) with a plane wave basis to further optimize the structure. In our work, the major calculations are performed with the Vienna ab initio simulation package (VASP) [19]. For exchange–correlation (XC) interaction, the local density approximation with the Ceperley–Alder prescription [20] (LDA model) and the generalized gradient approximation (GGA) of Perdew and Wang (PW91 model) are both used [21]. Electron–ion interaction is described by using the standard ultra-soft Vanderbilt pseudo-potentials (USPP) [22], distributed with the VASP package. The semi-core electrons of cation atoms (5d10 and 6s2 of Hg) are included explicitly in the calculations. The set of plane waves used is extended up to a kinetic energy cutoff of 300 eV. The large cutoff energy is required in order to achieve highly converged results within the USPP. Due to the large number of atoms in the unit cell, the structure optimization is done at the 0 point. And in the calculation of the electronic density of states (DOS), we use a 3 × 3 × 3 k-points mesh to sample the Brillouin zone in order to ensure highly converged results in the compounds. For the calculation of total energy, we use the tetrahedron method with Bl¨ochl corrections. The method also gives a good account for the electronic density of states. We also use an accurate algorithm during the calculations to obtain a highly converged force for the calculation.

to grow single-domain CdTe(211)B films on As-passivated Si(211) substrates. And for subsequent growth of mercury cadmium telluride films, CdTe(211)B layers can be grown on As-passivated Si(211) surfaces by molecular beam epitaxy (MBE) [11–13] and metal organic vapor phase epitaxy (MOVPE) [14–16]. But it is still quite difficult to get high-quality HgTe on Si surfaces, and the factors affecting the material quality are very complicated. As an alternative way, one considers whether amorphous HgTe can be grown on Si substrates. The present work aims to investigate the structural and electronic properties of HgTe in its amorphous configuration. The paper is organized as follows. Section 2 contains the details of the modeling and computational procedure. In section 3, the computed atomic configurations of amorphous HgTe are presented and discussed along with the electronic properties. Finally, in section 4, the main conclusion is presented. 2. Computational methods

For the structural and electronic properties, the necessary starting point is an atomistic model of amorphous HgTe. Based on the previously generated models, an initial configuration could be made by replacing the old atoms and rescaling the cell and allowing for atomic relaxation. The method to build the amorphous model may be called computation alchemy. So in this work, we present an amorphous HgTe supercell with 256 atoms. According to the continuous random network (CRN) concept [17, 18], the initial configuration of HgTe is prepared as follows.

3. Result and discussion 3.1. Structural properties

(i) A supercell with 256 atoms of amorphous silicon (a-Si) is formed by employing commercial software from Accelrys Inc. (ii) Considering the α-Si structure as a model structure, amorphous HgTe (a-HgTe) can be obtained by randomly replacing half of the silicon atoms by mercury atoms and the others by tellurium atoms. So the a-HgTe structure has 128 mercury atoms and 128 tellurium atoms. (iii) The lattice parameter is determined by the cell length of crystalline HgTe.

We summarize the major parameters of our a-HgTe models in table 1. Because the volume and shape of the cell are allowed to change in the relaxation process, the final structures are not exactly cubic, but nearly so. The PW91 calculation predicts a slightly bigger cell, and the cell is closer to a cube. From the atomic coordination, it can be found that our models follow the 8−N rule. The average coordination of our model structure is 3.97 for the LDA calculation and 3.86 for the PW91 calculation. They are both close to the standard values based on 8−N constraints (the average coordination hri is calculated 2

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

Figure 1. Distribution functions of structure parameters of a-HgTe models. (a) Radial distribution functions (RDFs) and (b) partial pair

correlation functions (PPCFs) of a-HgTe models showing the distribution of the atoms. (c) Angle distributions representing the characteristics of local structures of our models.

˚ the have a broader and weaker second peak. Beyond the 10 A, functions all tend to be constant. The result indicates that there is a uniform probability of finding atoms at a large distance, and the structure gradually transforms from being ‘ordered’ to being ‘disordered’. Thus, Hg–Te pairs produce the dominant contribution to the first peak of the total RDF, and the homopolar pairs constitute the second broad peak in the total RDF. In ˚ particular, homopolar pairs exhibit weak peaks below 3 A (marked by arrows in figure 1(b)). They both suggest that there are still a number of wrong bonds in our models, and there is an wrong bond rate of about 10%. The following electronic property shows that such kind of structure is responsible for some of the electronic tail states. Overall, the difference in coordination distribution and the distribution function is negligible, and it does not cause any significant change in structures. Thus, we can conclude that the two models are consistent with each other. To our knowledge, no reports based on experiments have been published which describe the structural properties of a-HgTe. However, according to results of x-ray diffraction (XRD) investigations of Hg0.78 Cd0.22 Te [23], our models are in reasonable agreement with the experimental data. Next, we discuss the Te–Hg–Te and Hg–Te–Hg angles to better understand the network of our models. The angle distributions are plotted in figure 1(c). Both models yield major peak positions close to θT = 109.47◦ for both angles; this is the characteristic bond angle of a tetrahedral structure. Over 75% of all bond angles are distributed between 90◦ and 120◦ . The Te-Hg–Te angles have much sharper peaks around

as hri = 4XHg + 4XTe ; XHg and XTe are the concentrations of Hg and Te atoms). For both models, the majority of Hg and Te are fourfold. Apart from that, it can be seen that threefold and fivefold atoms also play an important role in the system. The atomic numbers of threefold and fivefold coordination can reach from 10% up to 26%. On analysis, it can be found that they have a significant relationship with the localized states of the system. Due to the absence of long-range order, distribution functions, such as the radial distribution functions (RDFs) and the partial pair correlation functions (PPCFs), are usually used to represent the structural properties of disordered systems. The calculated total RDFs of the a-HgTe models are shown in panel (a) of figure 1. The distributions of different models’ RDFs are similar. In the LDA calculation, the first sharp peak ˚ and the first minimum is at 3.35 A. ˚ For is at about 2.79 A ˚ and the PW91 calculation, the first peak is at about 2.85 A ˚ the first minimum is at about 3.48 A. The second broad peak ˚ and 4.73 A ˚ for the LDA calculation and is at about 4.47 A the PW91 calculation, respectively. Generally, the RDFs of the models obtained by different XC functions are almost identical. The PPCFs are plotted in figure 1(b). Hg–Te pairs ˚ and 2.86 A ˚ in the LDA show a strong first peak at 2.79 A calculation and the PW91 calculation, respectively. For Te–Te pairs in the LDA model and the PW91 model, the first peaks ˚ and 4.77 A, ˚ are relatively broader and centered near 4.64 A respectively. For Hg–Hg pairs, the LDA model displays a ˚ while the PW91 model shows broad peak at about 4.25 A, bimodal structures of equivalent intensity peaks at 4.35 and ˚ Around 8 A, ˚ the PPCFs of Te–Te and Hg–Hg pairs all 4.65 A. 3

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

Figure 2. Projected density of states for (a) the LDA model and (b) the PW91 model. Inverse participation ratio (IPR) analysis for (c) the

LDA model and (d) the PW91 model. Together with the total DOS, the total IPR is displayed in the first panel of each model. The projected IPRs for both models according to different species are shown in the bottom two panels. Large IPR implies strong localization. The inset panels enlarge the situation near the bandgap. The Fermi level is at 0 eV.

θT for both models. In both models, over half of the Te–Hg–Te angles are distributed between 100◦ and 120◦ . However, around θT , the Hg–Te–Hg angle distribution is uniform, and from 90◦ to 120◦ , every 10◦ interval, there are about 20% of Hg–Te–Hg angles. Thus, the average value of Hg–Te–Hg angles is 105.39◦ for the LDA model and 105.87◦ for the PW91 model. For Te–Hg–Te angles, the average is a little greater, 109.03◦ for the LDA model and 109.64◦ for the PW91 model. Therefore, it can be concluded that the Te and Hg atoms tend to form tetrahedral units. Hence a-HgTe retains strong characteristics of its crystal short-range order and tends to form a tetrahedral arrangement. In addition, there is a prepeak or shoulder lower than 90◦ (marked by black arrows), implying the different sites of atoms in the models. The following discussion of electronic properties shows that the distortions are responsible for some of the electronic tail states.

a large contribution to the conduction band tail. The large proportion of p states in the valence bond model suggests that the local bond angle distortion is taken into account. Interestingly, there is a bandgap of 0.36 eV for the LDA model and 0.49 eV for the PW91 model, separating the valence and conduction bands, quite different from the situation in c-HgTe. The bandgaps obtained from our structural models are smaller than the experimental value of 0.8 eV [24], since the DFT calculation underestimates the gap, and in view of the topological structure, a-HgTe still retains some characteristic of its crystalline phases. Nevertheless, one may ask whether the gap is from the critical effect of topology distortion and if there are defect states in both sides of deep bands. Therefore, it is of interest to discuss the Kohn–Sham orbitals to gain insight into the defect states and energy levels. To quantify the localization of states, we present a discussion of the inverse participation ratio (IPR) for both P 2 , where q (E) is the structural models. I(E) = N [q (E)] i i=1 i Mullikan (point) charge residing at an atomic site i for an eigenstate with energy eigenvalue E, and it is normalized P ( N q (E) = 1, with N being the total number of atoms in i=1 i the supercell). The IPR is a measurement of the inverse of the site numbers involved in the state with energy E. For a uniformly extended state, the Mullikan charge contribution per site is uniform and equals 1/N. So, I(E) = 1/N. For an ideally localized state, only one atomic site contributes all the charge, and so I(E) = 1. This implies that a higher value of I(E) indicates that the states are accordingly more localized. In the same way, a lower value of I(E) indicates that the states are accordingly more expanded. The results are plotted in figure 2(c) and (d). For the total IPR, high

3.2. Electronic properties

The electronic properties are discussed through the electronic density of states (DOS) and the inverse participation ratio (IPR). Results are shown in figure 2. The DOSs are projected on different atomic species and orbitals. We plot the projected DOSs for both the LDA model and the PW91 model in panels (a) and (b). It is found that, for both structural models, the Te atoms form a large part of the valence and conduction tails, but a considerable part of the conduction tails comes from Hg atoms. Secondly, the projections into s, p, and d components show that the states of the valence band tail are mostly associated with p states, and the s and p states offer 4

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

assembling units repeatedly. The shorter the distance between Hg atoms is, the lower the energy of the corresponding states. Furthermore, for the PW91 model, at energy −5.25 eV, the value of the IPR is over 0.9. The result suggests that the m state is almost entirely localized on Hg65 with dangling and wrong bonds (figure 3(II)(m)). Moreover, the single wrong bonds between two Hg atoms are also associated with the high IPR states of the energy below −7 eV. In the LDA model, the l state is localized between Hg58 and Hg109 (figure 3(II)(l)), and the n state also localized between Hg58 and Hg109 atoms in the PW91 model, as shown in (figure 3(II)(n)).

IPRs are observed in states with energy lower than −5 eV for both models. Considering the DOS distribution, high IPR states are distributed at both sides of the DOS peaks. Then we can project the total IPR onto different species; the results are shown in the bottom two panels in figure 2. Comparing the IPR data, the states with energy lower than −9 eV come completely from Te atoms, and Hg atoms contribute to the region from −8.02 to −5.7 eV for the LDA model and from −7.71 to −5.23 eV for the PW91 model. However, there are several high IPR states at around −3 eV, and they are primarily from the Te–Te bond, according to further investigation. The eigenstates in the region from −5 eV to Fermi level are quite extended. The states of the valence band tail and the conduction band tail tend to be localized in the Te atoms. To relate the electronic structure to the topological units, we choose several electronic states (a–n in figure 2) with relatively high IPR and project them onto the individual atomic sites to determine the localization of the selected state on the specific atoms. The states with energy lower than −9 eV completely come from the s orbital of Te atoms since the s–s interaction is only influenced by the bond length. We present the characteristic atomic sites associated with the states a–n in the two panels in figure 3. The a state and c state correspond to the highest occupied state of the LDA model and the PW91 model, respectively. In the LDA model, the a state is associated with atoms Te56 and Te34, with the surrounding Hg atoms, forming a Hg–Te–Hg bond angle mostly around 90◦ . The b state is mainly distributed on the Te2 and Te96 atoms, with the energy being a little bit lower than that of the a state, and also with some small Hg–Te–Hg angles. In the PW91 model, the Te atoms Te15, Te117, and Te123 contribute mostly part of the c state, and the d state is much related to the atoms Te30, Te31, and Te96. Around these atoms, there are a lot of the same small bond angles. Thus, the states of the valence tail are related to Te atoms with distorted angles. Finally, to understand the electronic characteristics of defects in the amorphous phrase, we further discuss the high IPR state with lower energy. For the LDA model, the e state is at −3.21 eV and it is localized at the wrong bond between ˚ A similar defect Te100 and Te115 with a length of 2.766 A. can also be found in the PW91 model, which is marked as the ˚ Besides that, in g state with a little longer length of 2.792 A. ˚ between the PW91 model, the wrong bond of length 2.806 A Te71 and Te36 causes the f state at −2.7 eV. All the high IPR states in the delocalized electronic regions are related to the ˚ Te homopolar pairs and the bond lengths are around 2.85 A, corresponding to the weak peak in the PPCF of Te–Te. In figure 3(II), we present the Hg assembling units related to the states from h to n. For the LDA model, the two assembling units shown in panel (h) mainly contribute to the h states. In the PW91 model, the i state is localized on Hg125, for which four neighbors are almost in the same plane (figure 3(II)(i)), and the j state at −5.05 eV is localized among Hg73, Hg83, and Hg117. In addition, in the LDA model, the k state is greatly localized on Hg102, which is coplanar with the four surrounding atoms (figure 3(II)(k)). It can be observed that there are threefold rings of Hg atoms in the

4. Conclusion

Based on the CRN concept, we establish an initial a-HgTe configuration by randomly replacing atoms in the a-Si structure. We use different XC functions in our optimization, and then two a-HgTe atomistic models are created, namely the LDA model and the PW91 model. It can be observed that the PW91 model predicts a similar amorphous structure compared with the LDA model. But the LDA model produces a slightly bigger cell. The coordination results indicate that both models follow the 8 − N rule and most of the atoms are fourfold. In addition, it is also found that there are a significant number of threefold and fivefold atoms in the system; this is related to the localized electronic states. The distribution functions of radial and bond angles confirm that most atoms in the structural network tend to be fourfold and form a tetrahedral structure. The fine structures of the radial and angle distribution functions indicate the distinct sites of atoms in the structural models, which are greatly related to the electronic localization. Based on calculations of the DOS and IPR, we discussed the electronic properties of our models. A similar DOS around the bandgap is obtained in the two models. It is shown that there is a bandgap of about 0.4 eV, which is quite different from the semimetal property of c-HgTe. The projected DOSs of our models indicate that, in the electronic structure, not only is the bond length variation considered, but also the bond angle distortions are taken in to account. The IPR result is used to quantify the electronic localization. High IPR states are mainly distributed at both sides of the DOS peaks. The tail states around the bandgap tend to be localized on Te atoms. Related atoms of tail and defect states have been discussed. The valence tail states are associated with the Te atoms with distorted angles. The defect states are related to the structural defects; for example, the localized states close to the Fermi level are related to the wrong bond between Te atoms, and the distortion structures of Hg atoms contribute to the defect states at lower energy. Acknowledgments

The authors acknowledge the support provided by the State Key Program for Basic Research of China (2013CB632705, 2011CB922004), the National Natural Science Foundation of China (10990104, 61290301), and the Fund of Shanghai 5

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

Figure 3. Atomic structural distributions of localized electronic states, corresponding to the states marked in figure 2. Gray atoms are Hg,

orange atoms are Te. (I) The electronic states localized on Te atoms. (a) Te11, Te50. and Te127 are associated with tail state a, (b) Te2 and Te96 are associated with tail state b, (c) Te30, Te96, and Te31 are associated with tail state c, (d) the defect state d is mainly localized at Te100 and Te115, (e) Te71 and Te36 are associated with state e, (f) Te 115 and Te100 are associated with state f. (II) The electronic states localized on Hg atoms. (g) Hg48 and Hg125 are associated with defect state g, (h) the defect state h is localized at Hg125, (i) state i is primarily distributed in the Hg atoms in this panel, (j) Hg125, Hg102, and Hg40 are associated with state j, (k) Hg109 and Hg58 are associated with state k; (l) state l is highly localized on Hg65, (m) Hg58 and Hg109 are associated with state m. 6

J. Phys.: Condens. Matter 26 (2014) 045503

H Zhao et al

Science and Technology Foundation (10JC1416100). The use of computational resources from the Shanghai and Tianjin Supercomputer Centers is acknowledged.

[15]

References [16] [1] Markowski R and Podgorny M 1992 Calculated optical properties of zincblende semiconductors ZnTe, CdTe and HgTe J. Phys.: Condens. Matter 4 2505 [2] Gashimzade F M, Babaev A M and Bagirov M A 2000 Energy spectra of narrow- and zero-gap-semiconductor quantum dots J. Phys.: Condens. Matter 12 7923 [3] Kim S-W and Sohn K-S 1996 Optical properties of a multiple quantum well in a HgTe/CdTe system J. Phys.: Condens. Matter 8 7619 [4] Qteish A and Needs R J 1991 On the valence band offset controversy in HgTe/CdTe superlattices J. Phys.: Condens. Matter 3 617 [5] K¨onig M, Wiedmann S, Br¨une C, Roth A, Buhmann H, Molenkamp L W, Qi X-L and Zhang S-C 2007 Quantum spin hall insulator state in HgTe quantum wells Science 318 766–70 [6] An X-T, Zhang Y-Y, Liu J-J and Li S-S 2012 Measurable spin-polarized current in two-dimensional topological insulators J. Phys.: Condens. Matter 24 505602 [7] Kane C L and Mele E J 2005 Z2 topological order and the quantum spin hall effect Phys. Rev. Lett. 95 146802 [8] Zou Y L, Zhang L B and Song J T 2013 Anomalous electron collimation in HgTe quantum wells with inverted band structure J. Phys.: Condens. Matter 25 075801 [9] He L et al Introduction to Advanced Focal Plane Arrays 1st edn (Beijing: National Defense Industry Press) p111 (in Chinese) [10] Dhar N K, Boyd P R, Martinka M, Dinan J H, Almeida L A and Goldsman N 2000 CdZnTe heteroepitaxy on 3 (112) Si: Interface, surface, and layer characteristics J. Electron. Mater. 29 748–53 [11] Varesi J B, Buell A A, Peterson J M, Bornfreund R E, Vilela M F, Radford W A and Johnson S M 2003 Performance of molecular-beam epitaxy-grown midwave infrared HgCdTe detectors on four-inch Si substrates and the impact of defects J. Electron. Mater. 32 661–6 [12] Rujirawat S, Almeida L A, Chen Y P, Sivananthan S and Smith D J 1997 High quality large-area CdTe(211)B on Si(211) grown by molecular beam epitaxy Appl. Phys. Lett. 71 1810 [13] Varesi J B, Bornfreund R E, Childs A C, Radford W A, Maranowski K D, Peterson J M, Johnson S M, Giegerich L M, de Lyon T J and Jensen J E 2001 Fabrication of high-performance large-format MWIR focal plane arrays from MBE-grown HgCdTe on 400 silicon substrates J. Electron. Mater. 30 566–73 [14] Niraula M, Yasuda K, Ohnishi H, Takahashi H, Eguchi K, Noda K and Agata Y 2006 Direct growth of high-quality thick CdTe epilayers on Si (211) substrates by

[17]

[18]

[19]

[20]

[21]

[22] [23]

[24]

7

metalorganic vapor phase epitaxy for nuclear radiation detection and imaging J. Electron. Mater. 35 1257–61 Shigenaka K, Matsushita K, Sugiura L, Nakata F and Hirahara K 1996 Orientation dependence of HgCdTe epitaxial layers grown by MOCVD on Si substrates J. Electron. Mater. 25 1347–52 Shigenaka K, Matsushita K, Sugiura L, Nakata F, Hirahara K, Uchikoshi M, Nagashima M and Wada H 1996 Orientation dependence of HgCdTe epitaxial layers grown by MOCVD on Si substrates J. Electron. Mater. 25 1347–52 Shevchik N J, Tejeda J and Cardona M 1974 Densities of valence states of amorphous and crystalline III–V and II–VI semiconductors Phys. Rev. B 9 2627–48 Tu Y, Tersoff J, Grinstein G and Vanderbilt D 1998 Properties of a continuous-random-network model for amorphous systems Phys. Rev. Lett. 81 4899–902 Kresse G and Hafner J 1993 Ab initio molecular dynamics for liquid metals Phys. Rev. B 47 558–61 Kresse G and Hafner J 1994 Ab initio molecular-dynamics simulation of the liquid–metal–amorphous–semiconductor transition in germanium Phys. Rev. B 49 14251–69 Kresse G and Furthm¨uller J 1996 Efficiency of ab initio total energy calculations for metals and semiconductors using a plane-wave basis set Comput. Mater. Sci. 6 15–50 Kresse G and Furthm¨uller J 1996 Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set Phys. Rev. B 54 11169–86 Ceperley D M and Alder B J 1980 Ground state of the electron gas by a stochastic method Phys. Rev. Lett. 45 566–9 Perdew J P and Zunger A 1981 Self-interaction correction to density-functional approximations for many-electron systems Phys. Rev. B 23 5048–79 Perdew J P, Chevary J A, Vosko S H, Jackson K A, Pederson M R, Singh D J and Fiolhais C 1992 Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation Phys. Rev. B 46 6671–87 Perdew J P, Chevary J A, Vosko S H, Jackson K A, Pederson M R, Singh D J and Fiolhais C 1993 Erratum: atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation Phys. Rev. B 48 4978 Vanderbilt D 1985 Optimally smooth norm-conserving pseudopotentials Phys. Rev. B 32 8412–5 Li X, Kong J, Wang G, Yu L, Kong L, Yang L, Qiu F, Li C and Ji R 2010 The effect of annealing on the microstructure and photosensitivity of amorphous MCT films Infrared Technol. 32 255–8 Kong J, Wang S, Kong L, Zhao J, Ma Y, Wang G, Li X, Yang L, Zhang P and Ji R 2009 Studies of RF magnetron sputtered amorphous HgCdTe films Proc. SPIE 7383 73833Y Yu L, Shi Y, Deng G, Li X, Yang L and He W 2011 The research on photoelectrical properties of amorphous HgTe thin films Infrared Technol. 33 190–94

Ab initio investigation of the structural and electronic properties of amorphous HgTe.

We present the structure and electronic properties of amorphous mercury telluride obtained from first-principle calculations. The initial configuratio...
2MB Sizes 0 Downloads 3 Views