Sebania Libertino

The erbium‐impurity interaction and its effects on the 1.54 μm luminescence of Er3+ in crystalline silicon

We have studied the effect of erbium‐impurity interactions on the 1.54 μm luminescence of Er3+ in crystalline Si. Float‐zone and Czochralski‐grown (100) oriented Si wafers were implanted with Er at a total dose of ∼1×1015/cm2. Some samples were also coimplanted with O, C, and F to realize uniform concentrations (up to 1020/cm3) of these impurities in the Er‐doped region. Samples were analyzed by photoluminescence spectroscopy (PL) and electron paramagnetic resonance (EPR). Deep‐level transient spectroscopy (DLTS) was also performed on p‐n diodes implanted with Er at a dose of 6×1011/cm2 and codoped with impurities at a constant concentration of 1×1018/cm3. It was found that impurity codoping reduces the temperature quenching of the PL yield and that this reduction is more marked when the impurity concentration is increased. An EPR spectrum of sharp, anisotropic, lines is obtained for the sample codoped with 1020 O/cm3 but no clear EPR signal is observed without this codoping. The spectrum for the magnetic...

The effects of oxygen and defects on the deep-level properties of Er in crystalline Si

We have investigated the electronic properties of Er in crystalline Si using deep‐level transient spectroscopy and capacitance‐voltage measurements. Erbium was incorporated by ion implantation in a p+‐n junction structure. In order to explore the role of oxygen and defects some samples were coimplanted with O and the annealing behavior of the deep‐level spectra was explored in the temperature range 800–1000 °C for annealing times ranging from 5 s to 30 min. We show that O‐codoping produces large modifications in the Er‐related deep‐level spectra and, in particular, a promotion from deep to shallow levels, thus enhancing the donor behavior of Er in Si. For erbium implanted in pure crystalline Si the spectrum is dominated by deep levels arising from Er‐defect complexes which are easily dissociated upon thermal annealing. In O‐coimplanted samples the formation of Er‐O complexes with a characteristic level at EC−0.15 eV is observed. These complexes form upon thermal annealing and are stable up to 900 °C. Thes...

Depth profiles of vacancy- and interstitial-type defects in MeV implanted Si

We demonstrate that the depth distribution of defects in MeV implanted n-type and p-type crystalline Si is severely affected by the impurity content of the material. Silicon samples with different concentrations of dopants (P or B) and intrinsic contaminants (i.e., C and O) were implanted with 1 or 2 MeV He ions to fluences in the range 2.5×108–1×1013/cm2. Using deep-level transient spectroscopy and spreading resistance measurements, we have identified the defects and determined their concentration and depth distribution. It is found that less than 4% of the defects generated by the beam escape recombination and are stored in electrically active, room temperature stable defect clusters, such as divacancies and carbon–oxygen pairs. When the concentration of these defects is much smaller than the doping level, their profile mirrors the initial defect distribution, as calculated by transport of ions in matter (TRIM), a Monte Carlo code. In particular, the profile presents a maximum at the same depth predicte...

Transition from small interstitial clusters to extended {311} defects in ion-implanted Si

We have investigated the transition from small interstitial clusters to {311} defects in ion-implanted Si. Czochralski Si wafers were implanted with 1.2 MeV Si ions to fluences in the range 1012–5×1013/cm2 and annealed at temperatures of 600–750 °C for times as long as 15 h. Photoluminescence and transmission electron microscopy analyses allowed us to analyze the transition of small interstitial clusters, formed by the agglomeration of the excess interstitials introduced by the beam, into {311} defects. It is found that {311} defects form only at fluences ⩾1013/cm2 and at temperatures above 600 °C. When {311} are observed in transmission electron microscopy, the luminescence spectrum is dominated by a sharp signal at 1376 nm which has been correlated with optical transitions occurring at or close to these defects. At lower temperatures or at lower fluence, no extended defects are observed in transmission electron microscopy and the luminescence spectrum present two broad signatures arising from carrier re...

Dark Current in Silicon Photomultiplier Pixels: Data and Model

The dark current behavior of the pixels forming the Si photomultiplier as a function of the applied overvoltage and operation temperature is studied. The data are modeled by assuming that dark current is caused by current pulses triggered by events of diffusion of single minority carriers injected from the peripheral boundaries of the active area depletion layer and by thermal emission of carriers from Shockley–Read–Hall defects in the active area depletion layer.

Design, fabrication, and testing of an integrated Si-based light modulator

We have fabricated and characterized a novel Si-based light modulator working at the standard communication wavelength of 1.5 /spl mu/m. It consists of a three-terminal bipolar mode field effect transistor integrated with a silicon rib waveguide on epitaxial Si wafers. The modulator optical channel is embodied within its vertical electrical channel. Light modulation is achieved moving a plasma of carriers inside and outside the optical channel by properly biasing the control electrode. The carriers produce an increase of the Si absorption coefficient. The devices have been fabricated using clean-room processing. Detailed electrical characterization and device simulations confirm that strong conductivity modulation and plasma formation in the channel are achieved. The plasma distribution in the device under different bias conditions has been directly derived from emission microscopy analyses. The device performances in terms of modulation depth will be presented.

Materials issues and device performances for light emitting Er-implanted Si

Abstract The mechanisms of photo and electroluminescence from Er-implanted crystalline Si have been investigated and the crucial issues for the achievement of higher efficiency have been identified. Photoluminescence experiments show that Er-related levels are the gateway for the energy transfer from the electronic system of the semiconductor to the internal 4f shell of the Er ions. Er excitation is in fact thought to occur by the recombination of an electron-hole pair bound to an Er-related level. Higher yield and reduced temperature quenching of the luminescence can be obtained by engineering of the properties of these levels by codoping with O or other impurities. Room temperature electroluminescence has been achieved from Er doped crystalline Si diodes under both forward and reverse bias. Under forward bias the same mechanism identified from photoluminescence experiments is operative and therefore similar requirements have to be met in order to improve efficiency. On the other hand a higher room temperature electroluminescence yield is obtained under reverse bias. In this case the energy transfer occurs by impact excitation of the Er ions by hot carriers. Crucial issues for excitation mechanisms are the proper design of the diode structure in order to optimize the hot carrier distribution and the increase of the fraction of incorporated ions which are efficiently excited.

Room-temperature diffusivity of self-interstitials and vacancies in ion-implanted Si probed by in situ measurements

We have determined the room-temperature diffusivity of self-interstitials and vacancies in Si. Silicon p+−n junctions were realized in n-type epitaxial Si wafers, having an O and C content ⩽1015/cm3, and implanted at room temperature with 2.5 MeV He ions to fluences in the range 1×109–1×1012/cm2. The junctions were reverse biased at −30 V, in order to embody the entire damage profile of the ion in the depletion layer, and in situ leakage measurements were performed during and just after implantation. It is found that the leakage current increases monotonically during implantation while, at the beam turn off, it decreases by about a factor of 2 for times as long as 1 day. Ex situ deep level transient spectroscopy measurements show that the main contribution to leakage current is due to the deep levels introduced in the band gap by phosphorous–vacancy and divacancy complexes. This allowed us to associate the leakage current reduction at the beam turn off to the recombination of vacancy-type complexes by res...

Design and performance of an erbium-doped silicon waveguide detector operating at 1.5 /spl mu/m

A new concept for an infrared waveguide detector based on silicon is introduced. It is fabricated using silicon-on-insulator material, and consists of an erbium-doped p-n junction located in the core of a silicon ridge waveguide. The detection scheme relies on the optical absorption of 1.5-/spl mu/m light by Er/sup 3+/ ions in the waveguide core, followed by electron-hole pair generation by the excited Er and subsequent carrier separation by the electric field of the p-n junction. By performing optical mode calculations and including realistic doping profiles, we show that an external quantum efficiency of 10/sup -3/ can be achieved in a 4-cm-long waveguide detector fabricated using standard silicon processing. It is found that the quantum efficiency of the detector is mainly limited by free carrier absorption in the waveguide core, and may be further enhanced by optimizing the electrical doping profiles. Preliminary photocurrent measurements on an erbium-doped Si waveguide detector at room temperature show a clear erbium related photocurrent at 1.5 /spl mu/m.

Miniaturizable Si-based electro-optical modulator working at 1.5 μm

Optoelectronic devices are considered the innovative element for the next generation of microelectronic integrated circuits. For this purpose, both active and passive devices—extremely miniaturized—must be implemented. We fabricated and electro-optical Si-based light intensity modulator working at 1.5 μm using a bipolar mode field-effect transistor integrated within a Si rib waveguide. The principle of operation is the light absorption by a plasma of free carriers that can be opportunely moved inside or outside of the device optical channel by properly changing the control bias. The devices, only 100 μm long, were fabricated using epitaxial Si wafers and standard clean room processing. The optical characterization at 1.48 μm in static conditions shows a modulation of ∼90% while the dynamic electrical characterization provides a switching time of ≈10ns (foreseen modulation frequency of hundreds of MHz). A modulation depth above 25% is observed for modulation frequency up to 300 kHz.