Far Infra‐Red Photoconductivity

Putley, E.H.

doi:10.1002/pssb.19640060302

Cited by 114 publications

(11 citation statements)

References 74 publications

(14 reference statements)

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“…The EL and magnetotransport measurements were performed with the sample mounted in the center of a superconducting magnet ͑adjust-able between 0 and 14 T͒. The emitted light was coupled by a copper light-pipe to a cyclotron resonance InSb detector 15,16 tunable by a small superconducting coil ͑0-2.5 T͒. The spectra are then recorded by tuning the detector magnetic field while leaving the sample magnetic field constant.…”

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Terahertz intersubband emission in strong magnetic fields

Blaser

Rochat

Beck

et al. 2002

Applied Physics Letters

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Electroluminescence in quantum-cascade structures based on vertical transitions is studied in a strong perpendicular magnetic field in the limit in which the cyclotron energy is larger than the intersubband transition energy. Cyclotron emission and a luminescence intensity enhancement up to a factor of 6 is observed in GaAs/AlGaAs and InGaAs/InAlAs vertical transition-based quantum-cascade structures.The physics of intersubband transitions in the farinfrared is very different from the mid-infrared, because the scattering mechanisms are not only controlled by optical phonons. At low temperature the main scattering mechanisms are electron-electron scattering 1-3 and interface roughness.4,5 A strong perpendicular magnetic field will break the in-plane dispersion of the subbands and create a ladder of Landau levels attached to each subband, which strongly modifies these scattering mechanisms by reducing the phase space.6,7 The electron-electron scattering has a maximum of efficiency for processes in which the energy of the individual electrons is conserved.8 Therefore antiresonant Landau level emission is an efficient way of quenching the nonradiative scattering. Due to this additional quantization, the system has strong analogies with quantum boxes. Depending on the magnetic field, intersubband Landau resonances arise when the Landau levels of each subband align with a Landau level of a different subband with a level index-change ␦nϭ1,2,3, . . . The condition for such a resonance is thenwhere E trans is the intersubband transition energy and c ϭeB/m* is the cyclotron energy. Coherent tunneling between intersubband Landau levels with different indices is forbidden in ideal cases, but these resonances are possible due to the scattering between the Landau levels. Such resonances have already been used to derive the energy spectrum. 9-11In this paper we explore the magnetic limit at which the cyclotron energy ប c is larger than the intersubband transition energy E trans ; for our samples, this is the case at about 9.3 T for GaAs material system and 5.9 T for InGaAs material system ͑for hϭ16 meV͒. The increase of the lifetime of the upper state of the transition in a structure based on a diagonal transition, 9 as well as the suppression of a sequential tunneling current in a three-barrier, two-well heterostructure, 12 and the enhancement of the electroluminescence ͑EL͒ in a vertical transition 13 have also been observed by applying such a perpendicular magnetic field.The structures were grown using molecular beam epitaxy and were designed to emit photons at energies of 15 and 16 meV. These vertical transition structures are based on either InGaAs/InAlAs lattice matched to an n ϩ -InP substrate or GaAs/AlGaAs lattice matched to a n-doped GaAs substrate and consist of 35 periods. The latter structure is in fact a copy of the first design which gave far-infrared EL, 14 but with a higher doping that enables large injection currents ͑the negative differential resistance appears here at j ϭ150 A/cm 2 at low temperature͒. The ...

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Terahertz intersubband emission in strong magnetic fields

Blaser

Rochat

Beck

et al. 2002

Applied Physics Letters

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“…A custom-made broadbanded photoconductive indium antimonide detector has been used as SMMW detector (24)(25)(26)(27) and is drawn in Fig. 6.…”

Section: C) the Submillimeter Wave Detectormentioning

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A Broadband Submillimeter Wave Spectrometer System with On‐Line Microcomputer Data Analysis

Schäfer

Winnewisser

1983

Ber Bunsenges Phys Chem

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E. Schafer and M. Winnewisser: A Broadband Submillimeter Wave Spectrometer System etc. 327 higher alcohols approach the "normal" value of k , = 18 J h o l has been explained by a decreasing degree of association [ 161.From the theorem of corresponding states [15,16] one would expect equal values of surface tension at equal relative distances from the critical point. We have calculated the surface tension at half the critical temperature for each alcohol (last row in Table 3). Within +2% a surface tension of 25 mN/m is found for all alcohols investigated.to critical temperatures is obeyed for a variety of liquids. Considering the homologous trend of the boiling points (Fig. 3) the value of rS, = 313.5 " C for n-hexanol (Ref.[12]) appears to be too low. No value for LS, exists for n-pentanol.E 5344 1970.Berlin 1957. Absorptionsspektren, Mikroweilen / Apparate und Methoden / GaseA submillimeter wave spectrometer operating in the frequency range 100 to 800 GHz has been constructed for the study of transient molecules in the gas phase. The instrument employs harmonic generation of millimeter wave frequencies and a He-cooled lnSb photoconducting detector. A high degree of flexibility is achieved using an exchangeable free-space Pyrex absorption cell and a microcomputer for on-line data analysis. The spectrometer can be operated in a free-running video mode together with a fast signal averager or phase-locked to a microwave reference with source modulation. It is shown that the reproducibility of line center frequency measurements up to 600 GHz is i. 10 kHz. Transitions with absorption coefficients of at least 3 . lo.-* cm-' can be detected in the range from 150 to 250 GHz. Ground state rotational transitions of OCS between 200 and 690 GHz are reported and analysed together with previous data.

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“…The electronic lifetime T1 1 1 follows directly from Eq. (2), (3) and dn1/dt = -t~2n1 + t1n2 (14) dn2…”

Section: Recentl~rtw~dif!erent Methcds Have Beenmentioning

confidence: 99%

Determination of landau level lifetimes in n-GaAs

Bluyssen

Maan

Wyder

1979

Solid State Communications

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The lifetime of electrons in the first excited Landau level of n-GaAs is determined from a combination of measurements of far infrared cyclotron resonance induced absorption and conductivity change. Values of T 1 of the order of io-8s for densities of excited electrons of 1011 cm-3 and a temperature dependence of T-2.7 are found. An upper limit for the N = 0 Landau level to donor recombination time of the order of iO9s was derived from pulsed conductivity measurements.

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Far Infra‐Red Photoconductivity

Cited by 114 publications

References 74 publications

Terahertz intersubband emission in strong magnetic fields

Terahertz intersubband emission in strong magnetic fields

A Broadband Submillimeter Wave Spectrometer System with On‐Line Microcomputer Data Analysis

Determination of landau level lifetimes in n-GaAs

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