Electric field enhanced electron emission from gold acceptor level and A-centre in silicon

Irmscher, K.; Klose, H.; Maass, K.

doi:10.1002/pssa.2210750146

Cited by 27 publications

(10 citation statements)

References 8 publications

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“…1 In the other group, mainly DLTS measurements, emission of charge carriers from defect levels has been investigated in fields up to 10 5 V/cm. The observed field stimulated emission and capture have been discussed in terms of Poole-Frenkel effect, 2-4 phonon assisted tunneling, 5 and a combination of both phenomena. [6][7][8][9][10] It is frequently emphasized that at high-field strengths the characteristic electric field dependence of the Poole-Frenkel effect does not fit well the experimental data.…”

Section: Ionization Of Deep Centers By Electric Fieldsmentioning

confidence: 99%

“…[6][7][8][9][10] It is frequently emphasized that at high-field strengths the characteristic electric field dependence of the Poole-Frenkel effect does not fit well the experimental data. [5][6][7][8][9]11 The well-known Poole-Frenkel effect describes the increase of the thermal emission rate of carriers in an external electric field due to the lowering of the barrier associated with their Coulomb potential ͓Fig. 1͑a͔͒.…”

Section: Ionization Of Deep Centers By Electric Fieldsmentioning

confidence: 99%

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Distinction between the Poole-Frenkel and tunneling models of electric-field-stimulated carrier emission from deep levels in semiconductors

et al. 2000

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The enhancement of the emission rate of charge carriers from deep-level defects in electric field is routinely used to determine the charge state of the defects. However, only a limited number of defects can be satisfactorily described by the Poole-Frenkel theory. An electric field dependence different from that expected from the Poole-Frenkel theory has been repeatedly reported in the literature, and no unambiguous identification of the charge state of the defect could be made. In this article, the electric field dependencies of emission of carriers from DX centers in Al x Ga 1Ϫx As:Te, Cu pairs in silicon, and Ge:Hg have been studied applying static and terahertz electric fields, and analyzed by using the models of Poole-Frenkel and phonon assisted tunneling. It is shown that phonon assisted tunneling and Poole-Frenkel emission are two competitive mechanisms of enhancement of emission of carriers, and their relative contribution is determined by the charge state of the defect and by the electric-field strength. At high-electric field strengths carrier emission is dominated by tunneling independently of the charge state of the impurity. For neutral impurities, where Poole-Frenkel lowering of the emission barrier does not occur, the phonon assisted tunneling model describes well the experimental data also in the low-field region. For charged impurities the transition from phonon assisted tunneling at high fields to Poole-Frenkel effect at low fields can be traced back. It is suggested that the Poole-Frenkel and tunneling models can be distinguished by plotting logarithm of the emission rate against the square root or against the square of the electric field, respectively. This analysis enables one to unambiguously determine the charge state of a deep-level defect.

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Section: Ionization Of Deep Centers By Electric Fieldsmentioning

confidence: 99%

Section: Ionization Of Deep Centers By Electric Fieldsmentioning

confidence: 99%

Distinction between the Poole-Frenkel and tunneling models of electric-field-stimulated carrier emission from deep levels in semiconductors

et al. 2000

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“…This allows us to rule out multiphoton absorption as well as light impact ionization and unambiguously indicates that the deep impurity ionization is here due to tunnel ionization in the optical field. Such processes have been experimentally and theoretically investigated in detail for the case of a static electric field [1][2][3][4][5][6].…”

Section: Phonon Assisted Tunnel Ionization Of Deep Impurities In the mentioning

confidence: 99%

“…The electric field produces an almost triangular energy barrier and electron tunneling through that barrier yield a total ionization probability of W(E) = W 0 exp(F/F c ) 2 , where F is the force acting on the electron in the electric field and F c is the characteristic force [2]. Tunnel ionization has been extensively studied in semiconductors subjected to static electric fields [1][2][3][4][5][6]. In the present paper we show that the same process may occur in an optical field of frequency u < uj v , where UJ V is the local vibration frequency at the impurity site.…”

Section: Phonon Assisted Tunnel Ionization Of Deep Impurities In the mentioning

confidence: 99%

Phonon assisted tunnel ionization of deep impurities in the electric field of far-infrared radiation

1993

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Ionization of semiconductor deep impurity centers has been observed in the far infrared, where photon energies are several factors of 10 smaller than the binding energy of the impurities. It is shown that the ionization is caused by phonon assisted tunneling in the electric field of the high power radiation. This optical method allows the investigation of the tunneling process at electric bias fields well below the threshold of avalanche breakdown. PACS numbers: 79.70.+q, 71.55.Jv, 72.20.Ht, 72.40.+W We report on the first observation of the photoionization of deep impurity levels in a semiconductor by a radiation field with photon energies much less than the ionization energy of impurities. The photoconductivity of gold and mercury doped germanium has been observed and investigated using a high power pulsed farinfrared (FIR) laser source. A photoconductive signal, rising exponentially with the incident power, could be detected in spite of the fact that the photon energy of the exciting radiation is several factors of 10 less than the binding energy of the impurities, Ei. The experimental results give strong evidence that the ionization of deep impurity centers by radiation with photon energy hu

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“…We see that for each temperature there exists a field interval within which the probability of photoionization depends on the electric field amplitude as exp(E 2 /E 2 c ). A comparison of experimental data on terahertz ionization of the Au impurity in Si at T = 300 K with earlier studies of the dependence of thermal ionization probability on a dc electric field, e(E), made by means of capacitive spectroscopy [55,56] showed that in both cases e(E) ∝ exp(E 2 /E 2 c ), with the values of E c differing by a factor of 1.5-2. This may be considered a good agreement between the results obtained by such different methods, if we take into account the field inhomogeneities present in a sample studied by DLTS.…”

Section: Phonon-assisted Tunnelling Ionizationmentioning

confidence: 80%

Tunnelling ionization of deep centres in high-frequency electric fields

Ganichev

Yassievich

Prettl

2002

J. Phys.: Condens. Matter

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Experimental and theoretical work on the ionization of deep impurity centres in the alternating terahertz field of high-intensity far-infrared laser radiation, with photon energies tens of times lower than the impurity ionization energy, is reviewed. It is shown that impurity ionization is due to phonon-assisted tunnelling which proceeds at high electric field strengths into direct tunnelling without involving phonons. In the quasi-static regime of low frequencies the tunnelling probability is independent of frequency. Carrier emission is accomplished by defect tunnelling in configuration space and electron tunnelling through the potential well formed by the attractive force of the impurity and the externally applied electric field. The dependence of the ionization probability on the electric field strength permits one to determine defect tunnelling times, the structure of the adiabatic potentials of the defect, and the Huang-Rhys parameters of electron-phonon interaction.Raising the frequency leads to an enhancement of the tunnelling ionization and the tunnelling probability becomes frequency dependent. The transition from the frequency-independent quasi-static limit to frequency-dependent tunnelling is determined by the tunnelling time which is, in the case of phononassisted tunnelling, controlled by the temperature. This transition to the highfrequency limit represents the boundary between semiclassical physics, where the radiation field has a classical amplitude, and full quantum mechanics where the radiation field is quantized and impurity ionization is caused by multiphoton processes. In both the quasi-static and the 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 tunnelling time and also shifts the boundary between the quasi-static and the frequency-dependent limits to higher frequencies.At low intensities, ionization of charged impurities may also occur through the Poole-Frenkel effect by thermal excitation over the potential well formed by the Coulomb potential and the applied electric field. Poole-Frenkel ionization precedes the range of phonon-assisted tunnelling on the electric field scale and

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Electric field enhanced electron emission from gold acceptor level and A-centre in silicon

Cited by 27 publications

References 8 publications

Distinction between the Poole-Frenkel and tunneling models of electric-field-stimulated carrier emission from deep levels in semiconductors

Distinction between the Poole-Frenkel and tunneling models of electric-field-stimulated carrier emission from deep levels in semiconductors

Phonon assisted tunnel ionization of deep impurities in the electric field of far-infrared radiation

Tunnelling ionization of deep centres in high-frequency electric fields

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