Dislocation-related Luminescence Research Articles

Luminescent and Structural Properties of Self-Implanted Silicon Layers in Relation to their Fabrication Conditions

Luminescent and structural properties of silicon layers with dislocation-related luminescence have been studied. Silicon ions (100 keV) were implanted into n-FZ-Si wafers at a dose exceeding the amorphization threshold by two orders of magnitude. The implantation was not followed by amorphization of the implanted layers. A post-implantation annealing resulted in the formation of luminescence centers and extended structural defects. Some fundamental aspects and specific features in the properties of dislocation-related luminescence lines and extended structural defects were revealed in relation to the annealing conditions.

Nanocrystal- and Dislocation-Related Luminescence in Si Matrix with InAs Nanocrystals

We have studied the influence of ion implantation and post-implantation annealing regimes on the structural and optical properties of silicon matrix with ion-beam synthesized InAs nanocrystals. (100) Si wafers were implanted at 25 and 500 ◦C, subsequently with high fluences of As and In ions. After implantation the samples were processed by furnace and rapid thermal annealing at 900, 950 and 1050 ◦C. A part of the samples implanted at 25 ◦C was additionally exposed to H+2 ions (100 keV, 1.2 × 10 cm−2 in terms of atomic hydrogen). This procedure was performed to obtain an internal getter. In order to characterize the implanted samples transmission electron microscopy and low-temperature photoluminescence techniques were employed. It was demonstrated that by introducing getter, varying the ion implantation temperature, ion fluences and post-implantation annealing duration, and temperature it is possible to form InAs nanocrystals in the range of sizes of 2–80 nm and create various concentration and distribution of different types of secondary defects. The last ones cause in turn the appearance in photoluminescence spectra dislocation-related D1, D2 and D4 lines at 0.807, 0.870 and 0.997 eV, respectively.

Identification of dislocation-related luminescence participating levels in silicon by DLTS and Pulsed-CL profiling

We present a study of the dislocation network that occurs in the space charge region of a Schottky diode, by means of DLTS and our recently developed cathodoluminescent (CL) technique called Pulsed-CL. The details of the Pulsed-CL technique are provided. We establish a correspondence between the CL spectra of dislocation-related luminescence in silicon in the vicinity of the so-called D1 band and levels determined from DLTS measurements. The centres responsible for the 815 meV CL component are related to dislocations cores while the centres responsible for the 795 meV CL component are related to some defects outside of the dislocation cores.

Structures responsible for radiative and non‐radiative recombination activity of dislocations in silicon

AbstractRegular dislocation networks (DN) formed by direct bonding of Si wafers actively participate in recombination of minority carriers. Besides nonradiative recombination (NRR), dislocation‐related luminescence (DRL), i.e. radiative recombination could be observed. We show that the type of recombination is defined by the type of the dislocations and the structure of the network. Screw dislocations are mostly DRL active, while NRR is mostly related to edge dislocations. Moreover, the DRL intensity strongly depends on the misalignment angle between the crystal orientations of both bonded wafers. There exists an optimal alignment between bonded Si wafers, for which the DRL intensity has a maximum. Such alignment could be used for dislocation based all‐Si light emitting devices in the future on‐chip optical communication components. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modulation of 1.5 μm dislocation-related luminescence emitted from a direct silicon bonded interface by external bias

Interfacial dislocation networks were formed in silicon by direct bonding technology. Cathodoluminescence and deep level transient spectroscopy measurements verified that the D1 luminescence at 1.5 μm is associated with carrier transitions via a dislocation-related deep level at 0.35 eV. Both the experiment and theoretical calculations demonstrate that application of an external bias voltage on the bonding interface increases the majority carrier density at this deep level, thereby enhancing the local dislocation-related luminescence. However, beyond a critical voltage, corresponding to saturation of the majority carrier occupancy, the luminescence intensity decreases, due to the reduction in minority carrier density.

Defect engineering in implantation technology of silicon light-emitting structures with dislocation-related luminescence

Results obtained in development of physical foundations of ion implantation technology for fabrication of silicon light-emitting structures (LESs) based on dislocation-related luminescence and intended for operation at wavelengths close to ∼1.6 μm are summarized. The development of the concept of defect engineering in the technology of semiconductor devices makes it possible to determine the fundamental aspects of the process of defect formation; reveal specific features of the emission spectra related to changes in the implantation conditions of Er, Dy, Ho, O, and Si ions and the subsequent annealing; and design light-emitting structures with a desirable spectrum of luminescent centers and extended structural defects. The technological conditions in which only a single type of extended structural defect (Frank loops, perfect prismatic loops, or pure edge dislocations) is introduced into the light-emitting layer are found, which enables analysis of the correlation between the concentration of extended defects of a certain type and the intensity of lines of the dislocation-related luminescence. The key role of intrinsic point lattice defects in the origination and transformation of extended structural defects and luminescent centers responsible for the dislocation-related luminescence is revealed. It is found that the efficiency of luminescence excitation from the so-called D1 centers, which are of particular interest for practical applications, varies by more than two orders of magnitude between structures fabricated using different technological procedures. High-efficiency silicon light-emitting diodes with room-temperature dislocation-related luminescence have been fabricated.

Structural and Luminescent Properties of Implanted Silicon Layers with Dislocation-Related Luminescence

Structural and luminescence properties have been studied in silicon layers with dislocation-related luminescence. Multiple room temperature implantation of oxygen ions with doses low than the amorphization threshold was carried out. Silicon ions with a dose exceeding the amorphization threshold by two orders of magnitude were implanted at a higher temperature (≥ 80°C). Both the implantations were not followed by the amorphization of the implanted layers. Annealing in a chlorine-containing atmosphere resulted in formation of extended structural defects and luminescence centers. Some regularities and peculiarities in the properties of the extended defects and dislocation-related luminescence lines were revealed in dependence on the implantation and annealing conditions.

Determination of the Origin of Dislocation Related Luminescence from Silicon Using Regular Dislocation Networks

The investigation of regular dislocation networks (DN) formed by direct wafer bonding suggests that the D1 and D2 peaks of dislocation-related luminescence (DRL) in silicon is linked to screw dislocations, whereas edge dislocations are responsible for D3 and D4 DRL peaks. Non-radiative recombination activity in DN could be attributed to edge dislocations and could be related to enhanced ability of these dislocations to getter impurity atoms. Obtained relation of DRL intensity with the density of screw dislocations suggests existence of the optimum twist angle for the wafer-bonding geometry for which the DRL intensity has a maximum. The dependence of DRL intensity on the spacing between screw dislocations has the maximum at about 7 nm. Reported radiative and non-radiative recombination properties of DN present substantial interest not only for possible LED applications in all-Si photonics but also for photovoltaics, since DNs represent a model system for grain boundaries controlling carrier lifetime in microcrystalline-Si material.

Electroluminescence from p-i-n structure fabricated using crystalline silicon on glass technology

Strong electroluminescence was detected at room temperature from a p-i-n structure fabricated using crystalline silicon on glass technology. The luminescence spectra at small to moderate carrier injection levels contains strong peak with maximum at energy position Eph∼0.8 eV. Additionally, a broad emission band in the range of energies 1 eV<Eph<1.16 eV appears at high injection levels. Obtained results suggest that the low energy peak can be attributed to dislocation related luminescence (DRL), while at least part of the high-energy emission band should be attributed to band-to-band transitions. A shift in the DRL peak position by the electric field present in the structure was observed. The shift is related to strong Stark effect. The relatively high efficiency of room temperature luminescence suggests the possibility for application of the structure for all-silicon light emitter.

Cathodoluminescence study of dislocation-related luminescence from small-angle grain boundaries in multicrystalline silicon

Dislocation-related luminescence from small-angle grain boundaries (SA-GBs) in multicrystalline Si was investigated by cathodoluminescence. D3 and D4 emissions were detected at SA-GBs with a misorientation angle of around 1°–1.5°, and D1 and D2 at SA-GBs with a misorientation angle of around 2°–2.5°. Electron beam-induced current investigations indicate that the former SA-GBs possess only shallow energy levels, while the latter possess both deep and shallow levels. The origins of D-line luminescence at SA-GBs are discussed in terms of dislocation structures.

Silicon based light emitters utilizing radiation from dislocations; electric field induced shift of the dislocation-related luminescence

Dislocation rich regions can be controllably formed at a certain location inside a silicon wafer. We studied the light emission properties of such regions located in an electric field of a p–n junction under different excitation conditions. It was found that the luminescence spectra of the dislocations are significantly influenced by the presence of the junction. The dislocation-related luminescence peak position appears red-shifted due to the built-in electric field. A suppression of that field by photo-generation of carriers or by applying a forward bias voltage at the junction leads to a gradual decrease in the energy position of the peaks. The dependence of the peak position on the electric field was found to be a quadratic function, similar to that observed for semiconductor nanostructures. We show that the shift of the peak position is due to the Stark effect on dislocation-related excitonic states. The characteristic constant of the shift, obtained by fitting the data with the quadratic Stark effect equation, was 0.0186 meV/(kV/cm) 2. The observed effect opens new possibilities for integration of a silicon based light emitter, combining the radiation from dislocations with a Stark effect based modulator.

Influence of electric field on spectral positions of dislocation-related luminescence peaks in silicon: Stark effect

Spectral positions of dislocation-related luminescence (DRL) peaks from dislocation loops located close to a p-n junction in silicon were shifted by carrier injection level. We suppose that the excitonic transition energies of DRL were reduced by an effective electric field at dislocation sites due to quadratic Stark effect (QSE). The field results from built-in junction field reduced by carrier injection. A constant of the shift, obtained from fitting of the data with QSE equation, was 0.0186meV∕(kV∕cm)2. The effect can explain the diversity of DRL spectra in silicon and may allow tuning and modulation of DRL for future photonic applications.

Influence of Cu contamination on dislocation related luminescence

AbstractThis work is devoted to investigation of Cu contamination on dislocation related luminescence (DRL) in Si. Cu is known to be a very fast diffuser with high solubility. Fz Si samples were plastically deformed at 950 °C up to dislocation density of about 107 cm–2. Cu diffusion was performed by diffusion at 950 °C from a quartz ampoule contaminated with Cu. The presence and concentration of luminescent copper (Cu PL) centers was evaluated from the excitation dependence of the copper bound exciton no‐phonon line (BE NP) line at 1.014eV, which was activated after annealing at 1100 °C and rapid quenching in the water. 10 minutes isochronous annealing of the samples in the temperature range 300–600 °C revealed quite a different behavior of D4 and D1/D2 lines. It was assumed that a strong decrease of D1/D2 line intensity in annealing interval 400–500 °C could be attributed to passivation of D1/D2 luminescence centers by Cu atoms. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Radiative properties of dislocations generated around oxygen precipitates in Si

AbstractGeneration of dislocations during the growth of oxygen precipitates has been used as an alternative way of introduction of dislocation‐related luminescence centers. For this purpose a multistep annealing of Cz Si samples with different initial concentrations of oxygen has been carried out. The analysis of defect density and structure was performed by optical microscopy (OM) and transmission electron microscopy (TEM). The dislocation‐related luminescence (DRL) appeared only after a growth stage, while its intensity strongly depended on the duration of the preliminary nucleation treatment. The duration of growth annealing had a strong influence on the spectral distribution of the DRL intensity. No correlation has been found between a particular defect density, defined by TEM, and the shape of luminescence bands. Therefore, it was concluded that the cause of the gradual DRL transformation is redistribution of oxygen, collected near dislocations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure and radiation properties of dislocations arising during oxygen precipitate growth in silicon

The structural and radiation properties of defects formed during oxygen precipitation in Czochralski-grown silicon (Cz-Si) has been investigated by the methods of transmission electron microscopy (TEM) and photoluminescence (PL). It has been shown that the spectral intensity of dislocation-related luminescence (DL) is considerably redistributed as precipitates grow. A comparison of the concentration of different types defects with the DL integral intensity has shown that the secondary defects, namely, dislocations punched out of precipitates, make a main contribution to DL. In this case, the spectral distribution and integral intensity of DL are related to the extension of dislocation loops. The results show the capability of optimization of the dislocation-generation process to increase the intensity of the D1 line for its use in optoelectronics.

Dislocation-related luminescence in single-crystal silicon subjected to silicon ion implantation and subsequent annealing

Implantation of silicon ions with an energy of 100 keV at a dose of 1 × 1017 cm−2 into n-type floatzone Si does not lead to the formation of an amorphous layer. Subsequent annealing in a chlorine-containing atmosphere at 1100°C gives rise to dislocation-related luminescence. The intensity of the dominant D1 line peaked at a wavelength of ∼1.54 μm grows as the annealing time is increased from 15 to 60 min.

Silicon LEDs with room-temperature dislocation-related luminescence, fabricated by erbium ion implantation and chemical-vapor deposition of polycrystalline silicon layers heavily doped with boron and phosphorus

Light-emitting diodes (LEDs) have been fabricated in which optically active centers are formed by implantation of erbium ions into silicon and subsequent high-temperature annealing in an oxidizing atmosphere and the p-n junction and the ohmic contact are formed by chemical vapor deposition of polycrystalline silicon layers doped with boron and phosphorus, respectively. The luminescent properties of the LEDs have been studied. Use of polycrystalline layers makes it possible to eliminate the losses in the bulk of the light-emitting Si:Er layer. These losses are inevitable if the conventional ion implantation and diffusion methods are employed. At 80 K, the variation of electroluminescence spectra in the spectral range of the dislocation-related luminescence with the drive current is well described if the spectrum is decomposed into three Gaussian components whose peak positions and widths are current-independent and amplitudes linearly increase with the current. At 300 K, a single peak is observed in the spectral range of the dislocation-related luminescence at ∼1.6 μm.

Application of Czochralski-grown SiGe bulk crystal as a substrate for luminescent strained quantum wells

Czochralski-grown Si1−xGex bulk crystal (x=0.085) was utilized as a substrate for strained Si-based quantum wells (QWs). The linewidth of the (400) x-ray rocking curve of the SiGe(100) substrate was comparable with that of the Si(100) substrate, and no peak splitting was observed in the line scan all over the substrate. Epitaxial growth of strained QWs designed as a couple of strained Si/strained Ge QWs have been attempted simultaneously on SiGe(100) and Si(100). Photoluminescence measurements revealed that the sample on SiGe(100) exhibits peaks from excitons confined in QWs without any dislocation-related luminescence in contrast to that on Si(100).

Dislocation-related luminescence in silicon, caused by implantation of oxygen ions and subsequent annealing

Multiple implantation of oxygen ions with energies of 0.1–1.5 MeV at doses of 7 × 1013−2 × 1014 cm−2 and subsequent annealing in a chlorine-containing atmosphere at 900°C for 4 h give rise to dislocation-related luminescence in p-Si. A p → n conductivity-type conversion is also observed in this case in the surface layer of Si, which indicates that electrically active donor centers are formed in the process. Preliminary heat treatment of wafers covered with an erbium-doped film of tetraethoxysilane (TEOS) in argon at 1250°C for 1 h does not preclude the appearance of dislocation-related luminescence, but affects the parameters of the dislocation-related lines (peak positions and intensities).

Investigation of stress-induced defects in shallow trench isolation by cathodoluminescence and Raman spectroscopies

We have applied cathodoluminescence (CL) and Raman spectroscopies to shallow trench isolation (STI) processes in large scale integration to investigate crystalline defects and stresses by extracting the wafer after each process. A sample with high standby leakage current clearly showed dislocation-related luminescence lines (D lines) in the regions surrounding the memory cell. These regions contain various sizes of active and field areas ranging from 0.5to5μm. However, a normal sample showed no D lines in any region through the STI processes. The D lines were observed after liner oxidation, which was performed after trench patterning. Raman microprobe measurements showed that the trench patterning process generated a large inhomogeneous stress distribution up to 200MPa in the regions surrounding the memory cell. The inhomogeneous stress distributions caused by the trench patterning and the subsequent thermal processes are likely the main causes of dislocations. A comparison between the D lines in the CL spectra and the stress measured by a Raman microprobe clarified the mechanism of generation of crystalline defects. We can thus optimize the process conditions in STI processes by these spectroscopic methods.