Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Jun 12;21(12):4067.
doi: 10.3390/s21124067.

Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents

Vitaly Leonidovich Malevich  1   2 , Pavel Aliaksandravich Ziaziulia  3 , Ričardas Norkus  4 , Vaidas Pačebutas  4 , Ignas Nevinskas  4 , Arūnas Krotkus  4
Affiliations

Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents

Vitaly Leonidovich Malevich et al. Sensors (Basel). .

Abstract

Terahertz radiation pulses emitted after exciting semiconductor heterostructures by femtosecond optical pulses were used to determine the electron energy band offsets between different constituent materials. It has been shown that when the photon energy is sufficient enough to excite electrons in the narrower bandgap layer with an energy greater than the conduction band offset, the terahertz pulse changes its polarity. Theoretical analysis performed both analytically and by numerical Monte Carlo simulation has shown that the polarity inversion is caused by the electrons that are excited in the narrow bandgap layer with energies sufficient to surmount the band offset with the wide bandgap substrate. This effect is used to evaluate the energy band offsets in GaInAs/InP and GaInAsBi/InP heterostructures.

Keywords: GaInAsBi/InP; MBE; THz; THz emission spectroscopy; THz pulse generation; ballistic electrons; band offset; heterojunction.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Experimental set-up of THz excitation spectra measurements.
Figure 2
Figure 2
THz electric field (a,b) and photocurrent (c,d) pulses measured at two different optical wavelength beams impinging on sample A from the InP substrate side (a,c) and from the GaInAs epitaxial layer side (b,d).
Figure 3
Figure 3
THz excitation spectra of GaInAs/InP (a) and GaInAsBi/InP (b) heterostructure samples measured for cases of the layer-side photoexcitation (empty green triangles) and the substrate-side photoexcitation (full red circles). Blue crosses show the Monte Carlo simulation results.
Figure 4
Figure 4
Results of the analytical calculations of different photocurrent components by use of Equations (10)–(13), for the excitation from the GaInAsBi layer side (a) or the InP substrate side (b) Blue crosses show the Monte Carlo simulation results.
Figure 5
Figure 5
THz electric field pulses calculated by MC method for three different femtosecond optical pulse photon energies. The heterostructure is illuminated from the GaInAsBi layer-side (a) or from the InP substrate side (b).
Figure 6
Figure 6
The MC calculated contributions of GaInAsBi layer (solid lines) and InP substrate (dashed lines) to the photocurrent for a heterojunction excited by femtosecond pulse optical radiation from the top layer (a) and from the substrate side (b); the blue and red lines correspond to the photon energies of 0.8 and 1.2 eV, respectively. The photocurrent in the substrate at 0.8 eV is zero.
See this image and copyright information in PMC

References

    1. Zhang X.-C., Auston D.H. Optoelectronic measurement of semiconductor surfaces and interfaces with femtosecond optics. J. Appl. Phys. 1992;71:326. doi: 10.1063/1.350710. - DOI
    1. WFisher W.M., Rand S.C. Optically-induced charge separation and terahertz emission in unbiased dielectrics. J. Appl. Phys. 2011;109:064903. doi: 10.1063/1.3561505. - DOI
    1. Kadlec F., Kužel P., Coutaz J.-L. Study of terahertz radiation generated by optical rectification on thin gold films. Opt. Lett. 2005;30:1402. doi: 10.1364/OL.30.001402. - DOI - PubMed
    1. Johnson K., Price-Gallagher M., Mamer O., Lesimple A., Fletcher C., Chen Y., Lu X., Yamaguchi M., Zhang X.C. Water vapor: An extraordinary terahertz wave source under optical excitation. Phys. Lett. A. 2008;372:6037–6040. doi: 10.1016/j.physleta.2008.07.071. - DOI
    1. Jin Q., Yiwen E., Gao S., Zhang X.C. Preference of subpicosecond laser pulses for terahertz wave generation from liquids. Adv. Photonics. 2020;2:015001. doi: 10.1117/1.AP.2.1.015001. - DOI

LinkOut - more resources