ZnS中Te等电子中心的时间分辨光谱研究

用时间分辨光谱研究了很大的Te组分范围内的ZnS_1-xTe_x（x=00 05—085）合金的发光动力学特性，结果表明：不同形态的Te等电子中心具有不同的辐射复 合寿命，从几个ns到几十个ns的范围内变化，当x＝015左右时，寿命达到最大值（约 40ns）.其物理机理源于不同的Te等电子中心具有不同的局域化特性.当Te组分较小时，等 电子中心从Te₁逐渐演变到Te₂，Te₃或Te₄ 时，相应发光寿命增加，表现出不断增强 的激子发光局域化特性；而当Te组分较大时，Te原子团变得较大，其局域势与基体原子势的 相互作用增强，等电子中心的局域化特性减弱，而基体价带扩展态特征变得明显起来，相应 发光寿命逐渐减小.还研究了激子束缚能随Te组分的变化以及发光强度随温度的变化关系， 所得结果进一步支持了时间分辨光谱研究所得到的结论. 关键词： ZnS 等电子中心 时间分辨光谱 局域态     

Excitation spectroscopy on the P,Q, R isoelectronic lines in indium doped silicon

Excitation spectroscopy by a tunable NaF: (F⁺₂)¹ color center laser was successfully applied to the isoelectronic center responsible for the P, Q, R lines in indium doped silicon. This was facilitated by the extremely high P line luminescence intensities achieved after the special heat treatment which was recently reported. We determined three highly excited levels at energies of 11.4 meV, 19.4 meV, and 36.4 meV above the P line upper state.     

Dislocation-related photoluminescence in silicon

Photoluminescence is studied in silicon, deformed in a well-defined and reproducible way. Usual deformation conditions (high temperature, low stress) result in sharp spectra of the D1 through D4 lines as recently described in the literature. New lines D5 and D6 emerge for predeformation as above and subsequent low-temperature, high-stress deformation. Another new sharp line, D12, is observed when both the familiar and the novel lines appear simultaneously. Annealing for 1 h atT _A 300 °C causes all new lines to disappear and the D1–D4 spectra to reappear. Quantitative annealing and TEM micrographs suggest that D5 is related to straight dislocations and D6 to stacking faults, whereas D1–D4 are due to relaxed dislocations. Photoluminescence under uniaxial stress shows that D1/D2 originate in tetragonal defects with random orientation relative to 100 directions, whereas D6 stems from triclinic centers, preferentially oriented — as are the D3/D4 centers. We conclude that the D3/D4 and the D5 and D6 defects are closely related, whereas the independent D1/D2 centers might be deformation-produced point defects in the strain region of dislocations.     

Iron-aluminum pairs in silicon

Iron-aluminum pairs in silicon are investigated with conventional and optically detected electron paramagnetic resonance (EPR). For the trigonal and orthorhombic pairs known from previous EPR measurements we found for the first time optical absorption bands by measuring their magnetic circular dichroism of the absorption (MCDA). Direct experimental evidence is presented for the configurational bistability of both pairs by showing that the MCDA of the trigonal configuration can be transformed into that of the orthorhombic configuration by the combined effect of light and temperature. A new trigonal pair was discovered by conventional EPR having the same EPR intensity as the known one. Total energy calculations of various (Fe_i-Al_s) pair configurations show that two trigonal (Fe_i-Al_s)⁰ pairs with different Fe_i-Al_s separations have almost the same binding energy and should occur with the same probability. Fe _i ⁺ is always on a tetrahedral interstitial site, while Al _s ^– is nearest neighbor along 111 in one pair, second nearest neighbor in the other one with one silicon lattice site in between.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

A second isoelectronic multiexciton center in annealed Czochralski silicon

A recently reported group of photoluminescence lines observed in thermally annealed Czochralski silicon is studied using photoluminescence, excitation, and transient spectroscopies. The properties of these lines are remarkably similar to those of another, higher energy, series reported earlier. As for this previous case, we conclude that the new lines result from bound exciton and bound multiexciton complex recombination on an inhomogeneously broadened distribution of isoelectronic binding centers.     

Complex photoluminescence decay characteristics of the in-related isoelectronic bound exciton in Si

We present detailed photoluminescence decay measurements on the long-lived P, Q, R lines seen in In-doped Si, which reveal that the transient behaviour of this system is far more interesting than had been previously thought. At temperatures below 10K a double exponential behaviour is observed in the decay curves of all P, Q, R related lines, the long-lived part having a decay constant of up to 3.4 ms at 1.2K. These measurements provide the first evidence that the In-related isoelectronic bound exciton has two distinct configurations, as does the closely related Tl centre.     

Zeeman spectroscopy of the Zn acceptor in InP

Magneto-spectroscopy to 17.5 T of the Zn acceptor impurity in InP in the Faraday configuration using unpolarised radiation is reported. Four components of the G line have been followed to higher fields than previously, allowing the g factors of the ground and the first excited states to be determined more reliably. The Zeeman splitting of the D line is reported—three principal components are evident. A hitherto unreported third series of Zeeman transitions is observed at energies just above the reststrahlen band.     

Infrared absorption spectrum of beryllium acceptors in silicon

Beryllium, when introduced into silicon by thermal diffusion, gives rise to several acceptor impurity centers. The infrared absorption spectrum of beryllium in silicon has been measured with a Fourier-transform spectrometer. The absorption spectrum observed clearly shows five different beryllium acceptor centers in silicon.     

Zeeman effect in the polarization spectroscopy of Na

The Doppler-free polarization spectrum of the D₁ line has been studied in fields of about 50 G and in zero field. Although the principal Zeeman resonances are resolved, the signals are confusing because of the very large number of cross-over resonances. Cross-over resonances also seriously distort well-resolved resonances in zero field. An interpretation is given, based on combining a first-order theory of optical pumping with the theory of Faraday rotation and dischroism.     

Enhanced photoluminescence in grooved silicon microstructures

Grooved silicon structures formed by anisotropic chemical etching of crystalline silicon (c-Si) wafers in alkaline solution and composed by c-Si walls and voids (grooves) with thicknesses of several micrometers were found to exhibit efficient photoluminescence after excitation with laser radiation at 1.06 μm. The photoluminescence emission which originates from the interband radiative recombination of charge carriers in c-Si walls was represented by a broad spectral band centered at 1.1 eV. Independently on the polarization direction of the excitation light the photoluminescence of grooved silicon structures was partially linear-polarized with the polarization degree of 0.15–0.24 along c-Si walls and the photoluminescence intensity was strongly enhanced in comparison with that of c-Si substrate. These experimental observations are explained by considering an enhancement of the photoluminescence excitation due to both partial light localization in c-Si walls and a low rate of the non-radiative recombination at surface defects on c-Si walls. The defect density could be modified by additional chemical treatment or thermal annealing, which resulted in significant changes of the photoluminescence intensity of the grooved Si structures. The obtained results are discussed in view of possible applications of grooved Si in optoelectronics and molecular sensorics.     

Zeeman spectroscopy of NO with the magnetospectrophone

Immersion of a spectrophone in a magnetic field gives an instrument (the magnetospectrophone or MSP) that can in combination with a laser source be used to detect and study gases showing a Zeeman effect. Experiments are described using a fixed tuned CO laser source with the MSP to observe the Zeeman spectrum of NO. Possible other uses include detection of free radicals and monitoring of stratospheric chemistry. The electric analog (the electrospectrophone or ESP) could be used to study the Stark effect.     

Micro‐photoluminescence spectroscopy on heavily‐doped layers of silicon solar cells

We report and explain the photoluminescence spectra emitted from silicon solar cells with heavily‐doped layers at the surface. A micro‐photoluminescence spectroscopy system is employed to investigate the total spectrum emitted from both the heavily‐doped layer and the silicon substrate with micron‐scale spatial resolution. The two regions of the device give rise to separate photoluminescence peaks, due to band‐gap narrowing effects in the highly‐doped layer. Two key parameters, the absorption depth of the excitation wavelength, and the sample temperature, are shown to be critical to reveal the separate signatures from the two regions. Finally, this technique is applied to locally diffused and laser‐doped regions on silicon solar cell pre‐cursors, demonstrating the potential value of this micron‐scale technique in studying and optimizing locally doped regions. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Chromium and chromium-boron pairs in silicon

Four different measurement techniques: EPR, NAA, DLTS, and luminescence were applied to characterize the properties of chromium in silicon. The solubility of chromium in silicon was determined and its pairing reaction with boron was studied. The energy level atE _c?0.23 eV was attributed to interstitial chromium and a second level atE _v+0.27 eV was correlated to chromium-boron pairs. The luminescence band of the chromium-boron pairs was clearly identified. The properties of chromium are compared with those of other transition metal impurities in silicon crystals.     

多孔硅的时间延迟光谱

利用时间延迟光谱技术测量了多孔硅的发光光谱. 实验结果表明,多孔硅的发光是复杂的动力学发光弛豫过程,时间延迟光谱测量技术在研究复杂动力学发光过程方面比稳态光谱测量方法更有效.     

New results on the Zeeman effect of phosphorus in silicon

We report variational calculations of the quadratic Zeeman effect of phosphorus impurity in silicon, which are compared to our experimental data for B⊥E and B⊥E. It is shown that a small variation of the ratio γ of the transverse and effective masses can lead to a good agreement between theory and experiment for the 2p₀ line. The shift of the central component of the 2p_± line has been found to depend on the polarization of the incident radiation and this fact has not yet been explained. It is also shown that the shift observed for the line ascribed previously to a 1s(A₁)→3d₀ transition can be consistent with this attribution, giving experimental evidence of its electronic nature.