Optical properties of a multiple quantum well in a HgTe/CdTe system

Abstract

A finite HgTe/CdTe superlattice with different dielectric media on either side of the surfaces is investigated by taking into account the wavefunction overlap between the interface states and plasmons. The unit cell of the finite HgTe/CdTe superlattice consists of two electronlike states and a heavy-hole-like state in HgTe and two light-hole-like states in CdTe. Using the random-phase approximation added with some assumptions, we have studied the densitydensity correlation function by considering the interface state with the wavefunctions overlapping with the electron-like states, the light-hole-like states and the heavy-hole-like states. We have calculated the collective excitation spectra of the intrasubband and the intersubband for both the bulk plasmons and the surface plasmons as a function of the number of unit cells. The Raman intensities due to bulk and surface plasmons are expressed by the relative value of the mode energy of the plasmons.

First-principles analysis for the modulation of energy band gap and optical characteristics in HgTe/CdTe superlattices

“…A measured near band edge absorption spectrum was generated for HgTe/ (Hg 0.15 Cd 0.85 Te) SLs and compared with the previous calculated spectra in ref. 43 and 61-64. The experimental and calculated absorption spectra are quite identical to each other and followed a similar trend with layer thickness, as discussed in our work.…”

“…31,[38][39][40] The strained-layer interfaces have been examined in heterojunctions like the HgTe/CdTe interfaces including the biaxial strain effects. 25,[40][41][42][43][44][45][46][47][48][49] Interestingly, in recent transport experiments 14,40 using a 70 nm-thick HgTe lm grown on a CdTe substrate, it was shown that the strain induces a band gap, rendering the system to a 3D-TI or a novel system with intermediate properties.…”

“…Theoretical efforts also predicted an occurrence of inversion in the band alignment of an HgTe layer thicker than 6.3 nm, and thereby this behavior was proved to be ideal for the observation of a quantum spin Hall insulator phase. [32][33][34][35][36][37][41][42][43][44][45] The HgTe/CdTe QW exhibited a quantum phase transition where the electronic structure changes from normal to invert state. In this regard, HgTe-CdTe semiconductors are once again under the spotlight now, owing to the topological insulating (TI) behavior of HgTe system.…”

“…The large band gap tunability of 2D HgTe renders it a suitable material for practical applications in spintronics and quantum computing at roomtemperature. 13,14,22,[32][33][34][35][42][43][44][45] For prospective technological applications, it is imperative to catch the physical behaviors of the (HgTe) n /(CdTe) n SLs. For this purpose, realistic calculations are reported to analyze in detail the electronic structures, band parameters, and optical properties of unstrained and strained (HgTe) n / (CdTe) n (n ¼ 2-4) SLs.…”

“…This could conduct to the electron-like and heavy-hole-like states in the HgTe layer and the light-hole-like states in the CdTe layer being well conned. [24][25][26][27][28][29][30][31][42][43][44][45][54][55][56][57][58][59][60][61] The fact is that the width of the band gap strongly depends on the hybridization of the interface states with the heavy-hole-like sub-bands. This implies that the interface states are signicant for examining the optical properties, such as the optical absorption, of the HgTe/CdTe SLs.…”