Semiconductor superlattice diodes for detection of terahertz photons: The role of hybridization of the plasma and polar-optical phonon modes

Abstract

The current (voltage) responsivity of the superlattice-based diode detectors in the terahertz frequency band which includes the region of the polar optical phonon frequencies has been analyzed theoretically. Within the framework of the equivalent circuit approach an electro-dynamical model which allows one to analyze the responsivity taking into account the plasmon polariton excitation both in the substrate and in the contact layers of the diodes has been suggested. It has been shown that the presence of the plasmon polariton excitation gives rise to strong features in the frequency dependence of the superlattice-based diodes responsivity, i.e. to the resonance dips and peaks at frequencies of hybridized plasmons and optical phonons. It has been suggested that by judicious engineering of the superlattice-based diodes it would be possible to enhance substantially their responsivity in the terahertz frequency band. I. INTRODUCTIONRecently, a significant progress in the development of various powerful sources of pulsed terahertz (THz) radiation has been reached. In this content one can mention the fast development of the optically pumped THz molecular lasers 1 , the high-power THz radiation sources from relativistic electrons 2 , the pulsed sub-terahertz and terahertz gyrotrons 3,4 , and the free electron lasers (FELs) 5-7 . These sources seem to be very promising in terms of a number of applications such as THz-wave imaging, biological sciences, and pump-probe studies of dynamical properties of materials 1-7 . In this regard, a number of new concepts of THz pulsed radiation detectors having a rather high sensitivity, a short time of response, and a wide dynamic range has been put forward.Among others we can refer to traditional Schottky diode detectors 8-10 , photon-drag detectors 1 , field effect transistors detectors 11 , THz range quantum well infrared photodetectors 12 , and ultra fast graphene-based THz detectors 13 .On the other hand, superlattice-based diodes have also received considerable attention for detection of the ultra short terahertz pulses 14 . Experimentally, the interaction of the THz fields with the miniband electrons in semiconductors superlattices that show a negative differential conductance at room temperatures have been 1 a)

The non-linear terahertz response of hot electrons in low-dimensional semiconductor superlattices: Suppression of the polar-optical phonon scattering

“…take place due to effects of screening and "anti-screening" of the terahertz fields 5 μ to 1 m μ leads to the increase of the responsivity by more than three orders of magnitude. In connection with this, we will analyze the influence of the POP scattering suppression on the high-frequency response of the superlattices for the samples with rather low lateral size.…”

“…In recent years, semiconductor superlattices have received considerable attention from the viewpoint of the creation of new detectors [1][2][3][4][5] , oscillators [6][7][8][9][10] and frequency converters [11][12][13] of the terahertz and sub terahertz radiation. In this regard, the study of new transport phenomena associated with the Bloch electron dynamics and the electron heating in superlattices appears to be very interesting.…”