T1andT2spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects

Abstract

A study of donor electron spins and spin-dependent electronic transitions involving phosphorous ( 31 P) atoms in proximity of the (111) oriented crystalline silicon (c-Si) to silicon dioxide (SiO 2 ) interface is presented for [ 31 P] = 10 15 cm −3 and [ 31 P] = 10 16 cm −3 at about liquid 4 He temperatures (T = 5 K − 15 K). Using pulsed electrically detected magnetic resonance (pEDMR), spin-dependent transitions between the 31 P donor state and two distinguishable interface states are observed, namely (i) P b centers which can be identified by their characteristic anisotropy and (ii) a more isotropic center which is attributed to E ′ defects of the SiO 2 bulk close to the interface. Correlation measurements of the dynamics of spin-dependent recombination confirm that previously proposed transitions between 31 P and the interface defects take place. The influence of these electronic near-interface transitions on the 31 P donor spin coherence time T 2 as well as the donor spin-lattice relaxation time T 1 is then investigated by comparison of spin Hahn-echo decay measurements obtained from conventional bulk sensitive pulsed electron paramagnetic resonance and surface sensitive pEDMR, as well as surface sensitive electrically detected inversion recovery experiments. The measurements reveal that both T 2 and T 1 of 31 P donor electrons spins in proximity of energetically lower interface states at T ≤ 13 K are reduced by several orders of magnitude.

Electrically detected spin echoes of donor nuclei in silicon

“…We have previously used this mechanism to readout electron spin states with coherence times exceeding 150 µs 19 , and to determine the state of the nuclear spin following transfer and classical storage of the electron spin state 11 . The donors we measure are not restricted to the interface, and are therefore not influenced by near interface defects 17,18 . As described in detail in reference 19, the electron coherence time is in this case limited by the trapping of conduction electrons into the D − state, a process which can be controlled by modifying the carrier density.…”

Slow Hopping and Spin Dephasing of Coulombically Bound Polaron Pairs in an Organic Semiconductor at Room Temperature

“…[9] were undertaken at low temperatures. In this Letter, we utilize electrically detected Hahn echo sequences [10,11] to directly measure the phase coherence time at room temperature, under conditions much more similar to those in which devices operate. The echo sequence provides the basis for a computational model to simulate polaron pair spin decoherence, allowing us to extract an estimate of the hopping transport time scale of polarons bound in polaron pairs in the organic semiconductor MEH-PPV.…”

“…The experiment is implemented as follows [11] [ Fig. 1(c)]: with the external static magnetic field B 0 defining the z axis and after approach of the steady state, which is dominated by triplet pairs due to the much longer triplet lifetime, an on-resonance microwave 2 pulse [13] is applied.…”

Electrical Detection of Coherent Nuclear Spin Oscillations in Phosphorus-Doped Silicon using Pulsed ENDOR

“…To gain a first physical picture, we here separately discuss the effects of the recombination time τ ap characteristic for antiparallel electron spin pairs, of the recombination time τ p characteristic for the parallel spin pairs, and of the polarization of the nuclear spin system. To independently quantify the recombination time τ ap , we performed an inversion-recovery type of experiment [17]. The observed decay can be described with a stretched exponential with a time constant of ≈ 7µs, which we identify with τ ap , and an exponent of ≈ 0.5.…”

“…1 by ±x), with the phase changed by 180 degrees for every shot, and subtracting consecutive traces, only resonant changes in the photocurrent are detected. To obtain a sufficient signalto-noise ratio, the experiment is repeated with a shot repetition time of 800 µs allowing the electron spin system to relax to its steady-state [15,17]. The recorded current transients are box-car integrated, resulting in a charge ∆Q that is proportional to the antiparallel spin pair fraction [ap] at the end of the microwave pulse sequence [13].…”