About the Mechanisms of Spin-Dependent Recombination in Semiconductors

Electron paramagnetic resonance of ensembles of phosphorus donors in silicon has been detected electrically with externally applied magnetic fields lower than 200 G. Because the spin Hamiltonian was dominated by the contact hyperfine term rather than by the Zeeman terms at such low magnetic fields, superposition states α |↑↓ + β |↓↑ and −β |↑↓ + α |↓↑ were formed between phosphorus electron and nuclear spins, and electron paramagnetic resonance transitions between these superposition states and |↑↑ or |↓↓ states are observed clearly. A continuous change of α and β with the magnetic field was observed with a behavior fully consistent with theory of phosphorus donors in silicon.

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“…combination model 6,7,8,9,20,21,22,34,35,36,37,38,39,40,41 to the four levels. The spin Hamiltonian of the system during EDMR is given by…”

Section: B Rf Power and Magnetic Field Dependencies Of The Phosphorus...mentioning

confidence: 99%

Electrical detection and magnetic-field control of spin states in phosphorus-doped silicon

et al. 2009

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“…The reported values of residual stress in BaTiO 3 thin films vary from +600 MPa(tensile) [1] to ±200 MPa(compressive). [12] Although, self-poling films are sometimes observed, theory predicts a spontaneous polarization in these films of only a few percent. Since the c/a ratio in the tetragonal form of BaTiO 3 is 1.0115, reorientation of ferroelectric domains in randomly oriented films may relieve 1.1 GPa stress, causing a self-poling effect.…”

Section: Methodsmentioning

confidence: 99%

Electrical and Structural Properties of Oxygen-Containing Silicon Annealed at 670-720 K Under High Stress

Kudla¹,

Misiuk

Panas

et al. 2002

Adv. Eng. Mater.

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The resonance curves (Fig. 3) have near 2 Oe width as it can be determined for 14 MHz frequency by the symmetrical shape of the curve, whereas at lower values the left wings of the plots shorten. Particularly, this is revealed for 1.7 MHz when the nearly monotonous slope is registered (Fig. 3). This transformation of the shape is attributed to the difference between the resonance value of the magnetic field H 0 and the spectral width. When the difference is negative the shape transformation occurs with a non-zero value of the SDR at H 0 =0. A similar result was predicted by Deigen and Roitsin in [13] where it was attributed to the inner field included in the Hamiltonian in contrast to Eqn. 5 which, nevertheless, yields the signal at the null constant field (Fig. 4c, d). The model assumes that such a signal existence which provided the period of the alternating field is of the same order of magnitude or lower as the pair lifetime. Then the electron spin is exposed to the alternating field for only some part of its period, which is equivalent to the action of a constant magnetic field inducing T 0 «S transitions.The measured values of the SDR peak generally follow the EPR position (Fig. 4), although it varies at various values of the alternating field. The shift can reach nearly 0.2 Oe at 0.2 Oe amplitude as is shown for 3.5 and 7 MHz (Fig. 4a, b). The KSM model corrected subject to band±defect transitions predicts this shift (Fig. 4c, d) which appears due to a mutual consistency of two parameters: the SDR rate (transition 4, Fig. 2) and the pair concentration (i.e. the level occupancy). As the resonance is approached the pair recombination rate changes giving rise to changes of the pair concentration. The latter, in turn, determines the recombination rate. This feed-back gives rise to a cutting off the net resonance curve, the resultant minimum being deviated from the net EPR peak position.The SDR amplitude tends to sub-linear dependence on the amplitude of the alternating magnetic field with a steeper slope for 14 and 7 MHz (when it nearly reaches saturation: Fig 3, inset) than at a lower frequency.An experimental study and theoretical analysis revealed peculiarities of the SDR spectra for HF and VHF ranges as follows: i) transformation of the spectral profile at low frequencies 1.7, 3.5 and 7 MHz; ii) existence of the spin-dependent signal at the absence of the constant magnetic field; iii) shift of the SDR peak as compared to EPR on average by 0.2 Oe.

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“…The unpaired electrons give rise to an electron paramagnetic resonance (EPR) signal [2,3] which can manifest itself as a spin-dependent current flow due to spin-dependent recombination (SDR) of the free carriers. [4,5] Much higher sensitivity of the SDR signal as compared with conventional EPR allows reduction of the frequency from the microwave range (usually applied for EPR) to a solenoid range [6,7] which allows use of various frequencies instead of only resonator frequency. A specific condition appears when the frequency is reduced to the VHF and HF range: the resonant value of the constant magnetic field and the amplitude of the alternating field are of the same order of magnitude (Fig.…”

mentioning

confidence: 99%

“…The basic concept of KSM model states that the recombination proceeds through the pair of paramagnetic states. The quantum mechanical theory for this mechanism is based on the Hamiltonian in its simplest form, which includes Zeeman terms only: [12] H À l B =2 h g I d I g II d II À Á H (1) g I,II are g-factors, r I,II are the Pauli spin matrices, subscripts I, II numerate the electrons belonging to a given pair, H is the magnetic field vector. This theory yields value of the SDR R s (H 0 , h~, s s , r, d, g) for the paired states as a function of H 0 ,h~± value of constant and amplitude of alternating magnetic fields; s s ± time constant of the spin-flip; g,d ± rates of the pair generation and dissociation.…”

mentioning

confidence: 99%

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Spin-Dependent Recombination in Strained Si Under Fields of 1-30 MHz Range

Kozonushchenko

Kislyuk²,

Barabanov

et al. 2002

Adv. Eng. Mater.

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Magnetic properties of dislocations are attributed to unpaired electrons in their cores (dangling bonds [1] ). The unpaired electrons give rise to an electron paramagnetic resonance (EPR) signal [2,3] which can manifest itself as a spin-dependent current flow due to spin-dependent recombination (SDR) of the free carriers. [4,5] Much higher sensitivity of the SDR signal as compared with conventional EPR allows reduction of the frequency from the microwave range (usually applied for EPR) to a solenoid range [6,7] which allows use of various frequencies instead of only resonator frequency. A specific condition appears when the frequency is reduced to the VHF and HF range: the resonant value of the constant magnetic field and the amplitude of the alternating field are of the same order of magnitude (Fig. 1). This presumes the time constants contributing to the total SDR signal: spin-flip time, the field period and time constants related to the respective defect-zone transitions are comparable. The associated resonances from conduction electrons, defect holes and valence band holes would distort the resultant SDR resonance. [8,9] We present a study of the overall SDR peak position and amplitude at low frequencies as a function of alternating magnetic field. Thus, spin-dependent current changes follow the recombination rate.The sample (cut from an n-type Si wafer deformed nonuniformly to get a p±n structure as described in refs. 10 and 11 with a dislocation density r»10 8 cm ±2 ) was mounted in a flow cryostat under the crossed fields at 10 C and a 10 V forward bias was distributed between the high resistant p-base and the p±n junction. The frequency of the electromagnetic field was 3.5, 7 and 14 MHz and the amplitude was modulated with rectangular pulses (field on and off) to register the spin dependent additive with lock-in amplifier at the modulation frequency of 0.57 kHz. The SDR signal was registered as the current change at the constant voltage and various magnitudes of the alternating field from 0.5±1.2 Oe. A time constant was determined from SDR amplitude versus the modulation frequency dependencies within the 0.57±30 kHz range at various temperatures. The recombination mechanism of the current flow is supposed to prevail: the voltage drops generally over the base length.We used the model based on the Kaplan-Solomon-Mott (KSM) mechanism of the pair SDR. The basic concept of KSM model states that the recombination proceeds through the pair of paramagnetic states. The quantum mechanical theory for this mechanism is based on the Hamiltonian in its simplest form, which includes Zeeman terms only: [12] H À l B =2 h g I d I g II d II À Á H (1) g I,II are g-factors, r I,II are the Pauli spin matrices, subscripts I, II numerate the electrons belonging to a given pair, H is the magnetic field vector. This theory yields value of the SDR R s (H 0 , h~, s s , r, d, g) for the paired states as a function of H 0 ,h~± value of constant and amplitude of alternating magnetic fields; s s ± time constant of the spin-flip; g,d ± r...

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About the Mechanisms of Spin-Dependent Recombination in Semiconductors

Cited by 9 publications

References 4 publications

Electrical detection and magnetic-field control of spin states in phosphorus-doped silicon

Electrical detection and magnetic-field control of spin states in phosphorus-doped silicon

Electrical and Structural Properties of Oxygen-Containing Silicon Annealed at 670-720 K Under High Stress

Spin-Dependent Recombination in Strained Si Under Fields of 1-30 MHz Range

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