Nonlinear terahertz response of HgTe/CdTe quantum wells

Abstract

Without breaking the topological order, HgTe/CdTe quantum wells can have two types of bulk band structure: direct gap type (type I) and indirect gap type (type II). We report that the strong nonlinear optical responses exist in both types of bulk states under a moderate electric field in the terahertz regime. Interestingly, for the type II band structure, the third order conductivity changes sign when chemical potentials lies below 10 meV due to the significant response of the hole excitation close to the bottom of conduction band. Negative nonlinear conductivities suggest that HgTe/CdTe quantum wells can find application in the gain medium of a laser for terahertz radiation. The thermal influences on nonlinear optical responses of HgTe/CdTe quantum wells are also studied.

Nonlinear optical response of a two-dimensional semi-Dirac system in the terahertz regime

“…As shown in [32][33][34], the authors considered the electron-LO-phonon interaction using the Green's-function method [32] or random impurities scattering in the linear response theory [33,34]. The relaxation time decrease with increasing temperature [34], which only shift the peak position towards high frequency at higher temperature and lower chemical potential [35].…”

Interband infrared photodetectors based on HgTe–CdHgTe quantum-well heterostructures

“…In the opposite case, the electron escape from the QWs is associated with the tunneling through the triangular barrier formed by the electric field. Using a simplified model for the characteristics of the vertical photodetectors using the photoexcitation from the localized states in the structure and the electron injection from the emitter (used previously in the papers on the standard QWIPs as well as in the GLIPs [19][20][21][22][23][24][25][26][27]), one can obtain for the photocurrent density in the QWIP j photo and its photodetector responsivity R = j photo /I ω ω…”

“…Therefore, the standard A 3 B 5 QWIPs cannot compete with the interband Cd-HgTe photodiodes (PDs) [3] in performance. The recent progress in the fabrication of CdHgTe QW heterostructures [16][17][18][19] provides an opportunity for a further enhancement of the CdHgTe photodetector technology. In this paper, we propose and evaluate the QWIPs using the interband transitions in the CdHgTe heterostructures, in particular, with the HgTe QWs.…”

Concepts of infrared and terahertz photodetectors based on vertical graphene van der Waals and HgTe-CdHgTe heterostructures

“…The competing technology is HgTe-CdHgTe quantum well (QW) PDs. The recent progress in the fabrication of HgTe-CdHgTe QW heterostructures [12][13][14][15] has provided a further enhancement of the CdHgTe photodetector technology. These two technologies open up new opportunities for IR and THz radiation detection.…”