Tunnel ionization of deep impurities by far-infrared radiation

Ganichev, Sergey; Yassievich, I. N.; Prettl, Wilhelm

doi:10.1088/0268-1242/11/5/006

Cited by 14 publications

(20 citation statements)

References 28 publications

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“…2a where experimental results obtained with AlGaAs:Te at T = 150 K are shown. In this quasi-static regime the electron tunnels at the momentary magnitude of the electric field in a time shorter than the period of oscillation and thus the electric field *In the case of charged impurities (all substitutional impuritie8 investigated) a deviation from the field dependence e(E) a exp(E2 /E*2c) can be seen in relatively low field strength (up to 1 kV/cm) where the defects are thermally ionized through the Poole-Frenkel effect and the ionization probability is proportional to e(E) a exp("/Ze 3 E/K/k B T) [14,[17][18][19].…”

Section: Experimental Results and Analysismentioning

confidence: 99%

“…Such a behavior has been observed for all materials at sufficiently high temperatures. In this quasi-static regime [14,19,20] the characteristic field, which can be determined experimentally, is given by E c * 2 = 3m*h/(τ2* 3e 2) with 71 = τ2. Thus the investigation of field dependence of ionization probability allows to determine the defect tunneling time τ2.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

“…Direct electron tunneling occurs at the crossing of the U 2 ε and U1 potential curves, where an electronic transition is possible without any change in the configuration coordinate. This effect, leading to weaker growth of the ionization probability in comparison to the field dependence of phonon-assisted tunneling, extrapolated to higher fields, determines the ionization process at very high fields [14,19,27]. (1)- (3) for all values of the energy of electron tunneling e for Ge:Cu at 4.2 K and frequencies used in the experiments taking into account phonon-assisted and direct tunneling but ignoring the Coulomb interaction.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

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Excitation of Deep Defects by Intense Terahertz Radiation

Ganichev

1999

Acta Phys. Pol. A

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An analysis is done of the ionization of deep impurity centers by -high--intensity terahertz radiation, with photon energies tens of times lower than the impurity ionization energy. Under these conditions, ionization can be described as direct tunneling and phonon-assisted tunneling in which carrier emission is accompanied by defect tunneling in configuration space and electron tunneling in the electric field of the radiation. Within a broad range of intensity, frequency, and temperature, the terahertz electric field of the radiation acts like a static field. For very high frequencies and low temperatures an enhancement of tunneling as compared to static fields was observed. The transition between the quasi-static and the high frequency regime is determined by the tunneling time. For the case of deep impurities this is the time of redistribution of the defect vibrational system which depends strongly on temperature and the impurity structure.

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Section: Experimental Results and Analysismentioning

confidence: 99%

Section: Experimental Results and Analysismentioning

confidence: 99%

Section: Experimental Results and Analysismentioning

confidence: 99%

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Excitation of Deep Defects by Intense Terahertz Radiation

Ganichev

1999

Acta Phys. Pol. A

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“…2 At not too low temperatures and not too high electric field strengths such phonon-assisted tunneling is the dominant ionization mechanism whereas at low temperatures or very high fields direct carrier tunneling from the ground state into the continuum controls the ionization process without participation of phonons. 3 In the case of deep impurities the tunneling time, which determines the transition from the quasistatic to the highfrequency regime, is the time of the redistribution of the defect vibrational system upon ionization by tunneling. 4 As long as phonons are involved in the ionization process, this time depends strongly on the temperature as well as on the details of the impurity potential structure.…”

Section: Introductionmentioning

confidence: 99%

Tunneling ionization of deep centers in high-frequency electric fields

et al. 2002

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A theoretical and experimental study of the tunneling ionization of deep impurities in semiconductors has been carried out for high-frequency alternating electric fields. It is shown that tunneling ionization occurs by phonon-assisted tunneling which proceeds at high electric field strengths into direct tunneling without involving phonons. In the quasistatic regime of low frequencies the tunneling probability is independent of frequency. Raising the frequency leads to an enhancement of the tunneling ionization. The transition from the quasistatic limit to frequency-dependent tunneling is determined by the tunneling time which, in the case of impurities interacting with thermal phonons, is controlled by the temperature. In both the quasistatic and high-frequency limits, the application of an external magnetic field perpendicular to the electric field reduces the ionization probability when the cyclotron frequency becomes larger than the reciprocal tunneling time.

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“…The ratio of the conductivity under irradiation to the dark conductivity s i ͞s d , which is proportional to the ionization probability, is plotted as a function of the square of the peak electric field strength E. The ionization probability at this temperature and this material is independent of radiation frequency and increases with rising E like exp͑E 2 ͞E observed for all materials at sufficiently high temperatures. In this case [11,12] the characteristic field is given by E c ͑3m ‫ء‬h ͞t 3 2 e 2 ͒ 1͞2 where m ‫ء‬ is the effective mass of the carrier and t 2 h͞2k B T 6 t 1 is the defect tunneling time. Here t 1 is of the order of the impurity vibration period, and the sign depends on the type of the impurity.…”

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confidence: 99%

Carrier Tunneling in High-Frequency Electric Fields

et al. 1998

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An enhancement of tunnel ionization of deep impurities in semiconductors in an alternating field as compared to static fields has been observed. The transition between the quasistatic and the highfrequency regime is determined by the tunneling time. For the case of deep impurities this is the time of redistribution of the defect vibrational system which depends strongly on temperature and the impurity structure. A theory of tunnel ionization of deep impurities by high-frequency fields has been developed. [S0031-9007(98) PACS numbers: 72.20.Ht, 72.40. + w The effect of high-frequency coherent radiation on tunneling in semiconductor superlattices and nanostructures has attracted considerable attention recently. The superposition of a static electric field and an alternating field causes a wealth of new phenomena as a result of photon assisted tunneling [1][2][3]. In all these cases tunneling is accomplished by a static electric field, and the radiation influences the barrier penetration probability. An intense radiation field, however, can, in fact, both generate the tunneling barrier and initiate tunneling. Such a tunneling process has been observed with the result that the highfrequency field acts like a static field and the tunneling probability does not depend on frequency [4]. The frequency independent tunneling, however, must be limited to frequencies V with Vt , 1, where t is the tunneling time. This has been shown in a number of theoretical works [5][6][7][8][9][10], but has never been explored experimentally. In contrast to static electric fields where the electron tunnels at a fixed energy, in alternating fields the energy of the electron is not conserved during tunneling. In this case the electron can absorb energy from the field, which should lead to a sharp increase of the tunneling probability with increasing frequency for Vt . 1.Here we report on the first experimental demonstration of this effect observed in tunneling ionization of deep impurities in semiconductors. We show that the transition from the quasistatic regime Vt , 1 to the high-frequency regime Vt . 1 occurs at terahertz frequencies. In the quasistatic regime the electron tunnels at the momentary magnitude of the electric field in a time shorter than the period of oscillation, thus the electric field acts like a static field. The ionization probability is independent of frequency and increases with rising field strength E like exp͑E 2 ͞E 2 c ͒ where E c is a characteristic field [4]. In the high-frequency regime the ionization probability, being characterized by the same field dependence, substantially increases with increasing frequency. In contrast to tunneling ionization of atoms, where only electron tunneling takes place [5], ionization of impurities in solids is accomplished by two simultaneous tunneling processes, electron tunneling and the redistribution of the vibrational system by defect tunneling. A theory of the process is developed showing for the first time that in this case the electron tunneling time is controlled by...

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Tunnel ionization of deep impurities by far-infrared radiation

Cited by 14 publications

References 28 publications

Excitation of Deep Defects by Intense Terahertz Radiation

Excitation of Deep Defects by Intense Terahertz Radiation

Tunneling ionization of deep centers in high-frequency electric fields

Carrier Tunneling in High-Frequency Electric Fields

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