Enhanced terahertz absorption of quantum wells sandwiched between heavily doped contacts based on micro-cavity resonance

Abstract

A novel high-efficiency microcavity structure of quantum wells sandwiched between periodic heavily Si-doped GaAs top contact gratings and bottom contact film has been proposed as the optical coupler of a terahertz quantum well photodetector (THz QWP). Similar to metal at visible light, highly doped semiconductors exhibit plasma frequencies at mid- and far-infrared wavelengths. The intersubband absorption spectra and electric field distribution of the microcavity THz QWP are calculated with the finite difference time-domain method. Our results indicate that the frequency of the surface plasmon polariton can be tuned to the microcavity resonant mode under an optimized structure and the intersubband absorption is efficiently enhanced by the microcavity structure. When the doping concentration of the contact exceeds 1018 cm−3, the intersubband absorption of the microcavity THz QWP at the response wavelength is over one order of magnitude higher than that of the standard 45° device. In addition, the angle of the incident light only influences the intensity of the absorptivity, indicating that the designed device was independent of the periodic surface structure.

Enhancement of wide-band trace terahertz absorption spectroscopy based on microstructures: a review

“…In 2020, H. M. Yang et al replaced the metal component with heavily doped contacts in the sandwich structure to boost the intersubband absorption through the microcavity resonant modes. 74 The photon absorption of the GaAs material is higher, with an enhancement of about 20 times compared to the standard structure. Additionally, the microcavity terahertz quantum well photodetector exhibits intersubband absorption at the interesting frequency, which is over one order of magnitude greater than the standard structure's absorption.…”

“…As a result, doped semiconductors exhibit permittivity values in the terahertz and microwave regions that are comparable to the results of metals in the optical frequencies. 74 One of the key advantages of utilizing a highly doped dielectric material is to circumvent the issue of higher absorption, commonly observed in traditional metal structures. By manipulating the carrier density, semiconductors exhibit modified dielectric properties, providing a more practical means to regulate the plasmon resonance.…”

Metasurface Photodetectors

“…Near field scattering is preferable to improve the responsivity of the photodetector by integrating plasmonic nanoantennas. However, the non-negligible Ohmic loss in metallic nanoantennas restricts further improvement of the responsivity, which can be reduced by replacing Nobel metals with a highly doped semiconductor [34]. Near field scattering also enables isotropic photodetectors (quantum well photodetector) to resolve linear polarization states with great extinction ratio.…”

Research progress in terahertz quantum-cascade lasers and quantum-well photodetectors

“…[84] In operation temperature, in 2015, Jia et al found that when a terahertz light beam with a power density of 819 W/cm 2 is introduced, the optical-noise-limit performance temperature of the terahertz QWP with a peak detection frequency of 5.5 THz can be increased to over 77 K, [82] which provides guidance and help for improving the operating temperature of terahertz QWP. The plasmon resonant [95] and the mico-cavity coupled [96] terahertz QWPs were realized by Zheng et al and designed by Yang et al, respectively. Finally, the progress of the performance of terahertz QWPs is shown in Table 3.…”