Quantum Confinement Effect of Thermoelectric Properties

제구철,Chang-Ho Cho 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1

Using the quantum confinement effect based on the conduction band model, we theoretically determine the optimal concentration for the best figure-of-merit in n-type Bi2Te3 quantum well structures. The Bi2Te3 system has polycrystalline structures that can be prepared by using powders of hot-pressed alloys. The enhanced figure-of-merit due to the quantum confinement is almost caused by the enhanced Seebeck coefficient and by improved resistivity. It results from competition between the strong intrinsic characteristic and the enhancement of the volume ratio of the concentration in the quantum-confined system. The optimum concentration for the best figure-of-merit in the system amounts to 2.1 × 10^11 cm^-2 at room temperature. Control of the carrier concentration, as well as the quantum confinement effect, is also a very important effect to optimize the figure-of-merit in low-dimensional systems. Using the quantum confinement effect based on the conduction band model, we theoretically determine the optimal concentration for the best figure-of-merit in n-type Bi2Te3 quantum well structures. The Bi2Te3 system has polycrystalline structures that can be prepared by using powders of hot-pressed alloys. The enhanced figure-of-merit due to the quantum confinement is almost caused by the enhanced Seebeck coefficient and by improved resistivity. It results from competition between the strong intrinsic characteristic and the enhancement of the volume ratio of the concentration in the quantum-confined system. The optimum concentration for the best figure-of-merit in the system amounts to 2.1 × 10^11 cm^-2 at room temperature. Control of the carrier concentration, as well as the quantum confinement effect, is also a very important effect to optimize the figure-of-merit in low-dimensional systems.

A Model for the InGaAs/InP Single Photon Avalanche Diodes with Multiple-Quantum Wells in the Charge Multiplication Region

H. S. Seo,S. H. Park,S. Kwak,안도열 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.2

In this work, we study the InP-InGaAs single photon avalanche diodes with multiple InGaAs quantum wells in the multiplication region for quantum information and communication. The compositions of InGaAs quantum wells are adjusted to give transition wavelength of 1.55. Simulation results show that three orders of magnitude improvement of dark count probability and an order of magnitude improvement of single photon quantum efficiency are expected with the adaption of multiple quantum-wells in the multiplication region. The improvement dark count probability is due to the difference of ionization coefficients for electrons and holes caused by the large difference between the conduction and valence band edge of multiple quantum-well layers inserted in the multiplication layer.

Investigation of detection wavelength of Quantum Well Infrared-Photodetector

S. H. Hwang,J. G. Lim,J. D. Song,J. C. Shin,D. C. Heo,W. J. Choi 한국진공학회(ASCT) 2015 Applied Science and Convergence Technology Vol.24 No.6

We report on GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) that can cover the spectral range of 3.6-25 ㎛. One advantage of the GaAs QWIPs is the wavelength tenability as a function of their structural parameters. We have performed a systematic calculation on the detection wavelength of a typical GaAs/AlxGa1-xAs multi-quantum-well photodetector, with the aluminum mole fraction (x) of AlxGa1-xAs barrier in the range of 0.15- 0.43 and the quantum-well width range from 30 to 60 Å. Design and fabrication of a QWIP based on GaAs/Al0.23Ga0.77As structure with 37 Å-thick well width has been carried out. The calculated operation wavelength of the QWIP is in a good agreement with the experimental data taken by photo response and activation energy calculation from thermal quenching of integrated photoluminescence.

Numerical Study of Strained GaAs 1−x N x /GaAs Quantum-Well Laser

M. Lahoual,A. Gueddim,N. Bouarissa 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.4

The optical gain of a strained GaAs 1−x N x /GaAs quantum-well laser has been calculated for a nitrogen concentration of 0.03 corresponding to a so-called dilute alloy. The eff ect of the density of carriers along with that of the quantum well width on the optical gain of the considered laser have been investigated and analyzed. Besides, the emitted wavelength has been also derived as a function of the quantum well width. Numerical results clearly show that by increasing the density of carriers and the quantum well width the optical gain is increased. The emitted wavelength is also enhanced as the quantum well width is augmented. The laser diode being studied here is shown to emit in the infrared-red region of the electromagnetic spectrum.

Investigation of detection wavelength of Quantum Well Infrared-Photodetector

Hwang, S.H.,Lim, J.G.,Song, J.D.,Shin, J.C.,Heo, D.C.,Choi, W.J. The Korean Vacuum Society 2015 Applied Science and Convergence Technology Vol.24 No.6

We report on GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) that can cover the spectral range of $3.6-25{\mu}m$. One advantage of the GaAs QWIPs is the wavelength tenability as a function of their structural parameters. We have performed a systematic calculation on the detection wavelength of a typical $GaAs/Al_xGa_{1-x}As$ multi-quantum-well photodetector, with the aluminum mole fraction (x) of $Al_xGa_{1-x}As$ barrier in the range of 0.15-0.43 and the quantum-well width range from 30 to 60 $60{\AA}$. Design and fabrication of a QWIP based on $GaAs/Al_{0.23}Ga_{0.77}As$ structure with $37{\AA}$-thick well width has been carried out. The calculated operation wavelength of the QWIP is in a good agreement with the experimental data taken by photo response and activation energy calculation from thermal quenching of integrated photoluminescence.

Intraband Relaxation Time in Compressive-Strained Quantum-Well Lasers

PARK, Seoung Hwan,Masahiro, ASADA,Koji, KUDO,Shigehisa, ARAI 대구효성가톨릭대학교 자연과학연구소 1992 基礎科學硏究論集 Vol.1992 No.1

Intraband relaxation time is investigated theoretically for a compressive-strained quantum well by considering carrier-carrier and carrier-longitudinal optical (LO) phonon scattering mechanisms. It is found that the spectral broadening factor decreases from 10 meV in the lattice-matched quantum well to about 5 meV in the strained quantum well. This is mainly attributed to the reduction of the hole effective mass due to strain effect. Dependence of the intraband relaxation time on carrier density and well width is also discussed.

Investigation of detection wavelength of Quantum Well Infrared-Photodetector

Sung Ho Hwang,Jae Gu Lim,Jin Dong Song,Jae Cheol Shin,Du Chang Heo,최원준 한국진공학회 2015 Applied Science and Convergence Technology Vol.24 No.6

We report on GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) that can cover the spectral range of 3.6-25 μm. One advantage of the GaAs QWIPs is the wavelength tenability as a function of their structural parameters. We have performed a systematic calculation on the detection wavelength of a typical GaAs/AlxGa1-xAs multi-quantum-well photodetector, with the aluminum mole fraction (x) of AlxGa1-xAs barrier in the range of 0.15- 0.43 and the quantum-well width range from 30 to 60 Å. Design and fabrication of a QWIP based on GaAs/Al0.23Ga0.77As structure with 37 Å-thick well width has been carried out. The calculated operation wavelength of the QWIP is in a good agreement with the experimental data taken by photo response and activation energy calculation from thermal quenching of integrated photoluminescence.

Magneto-optical Measurements of Semiconductor Quantum Structures in Pulsed-magnetic Fields

Yongmin Kim 한국진공학회(ASCT) 2014 Applied Science and Convergence Technology Vol.23 No.1

Semiconductor quantum structures are often characterized by their energy gaps which are modified by the quantum size effect. Energy levels in semiconductors can be realized by optical transitions within confined structures. Photoluminescence spectroscopy in magnetic fields at low temperatures has proved to be a powerful technique for investigating the electronic states of quantum semiconductor heterostructures and offers a complimentary tool to electrical transport studies. In this review, we examine comprehensive investigations of magneto-excitonic and Landau transitions in a large variety of undoped and doped quantum-well structures. Strong magnetic fields change the diamagnetic energy shift of free excitons from quadratic to linear in B in undoped single quantum well samples. Twodimensional electron gas induced by modulation doping shows pronounce quantum oscillations in integer quantum Hall regime and discontinuous transition at ν=1. Such discontinuous transition can be explained as the formation of spin waves or Skyrmions.

Magneto-optical Measurements of Semiconductor Quantum Structures in Pulsed-magnetic Fields

Kim, Yongmin The Korean Vacuum Society 2014 Applied Science and Convergence Technology Vol.23 No.1

Semiconductor quantum structures are often characterized by their energy gaps which are modified by the quantum size effect. Energy levels in semiconductors can be realized by optical transitions within confined structures. Photoluminescence spectroscopy in magnetic fields at low temperatures has proved to be a powerful technique for investigating the electronic states of quantum semiconductor heterostructures and offers a complimentary tool to electrical transport studies. In this review, we examine comprehensive investigations of magneto-excitonic and Landau transitions in a large variety of undoped and doped quantum-well structures. Strong magnetic fields change the diamagnetic energy shift of free excitons from quadratic to linear in B in undoped single quantum well samples. Two-dimensional electron gas induced by modulation doping shows pronounce quantum oscillations in integer quantum Hall regime and discontinuous transition at ${\nu}=1$. Such discontinuous transition can be explained as the formation of spin waves or Skyrmions.

Magneto-optical Measurements of Semiconductor Quantum Structures in Pulsed-magnetic Fields

김용민 한국진공학회 2014 Applied Science and Convergence Technology Vol.23 No.1

Semiconductor quantum structures are often characterized by their energy gaps which are modified by the quantum size effect. Energy levels in semiconductors can be realized by optical transitions within confined structures. Photoluminescence spectroscopy in magnetic fields at low temperatures has proved to be a powerful technique for investigating the electronic states of quantum semiconductor heterostructures and offers a complimentary tool to electrical transport studies. In this review, we examine comprehensive investigations of magneto-excitonic and Landau transitions in a large variety of undoped and doped quantum-well structures. Strong magnetic fields change the diamagnetic energy shift of free excitons from quadratic to linear in B in undoped single quantum well samples. Twodimensional electron gas induced by modulation doping shows pronounce quantum oscillations in integer quantum Hall regime and discontinuous transition at ν=1. Such discontinuous transition can be explained as the formation of spin waves or Skyrmions.