Papers by Keyword: Defect Engineering

Abstract: In the past 20 years, the phase-change memory technology has achieved rapid development, of which alloys along the GeTe-Sb₂Te₃ pseudobinary line are the most extensively researched materials. In recent years, Sb₂Te₃-based materials start to attract the attention of researchers. A recent study has shown that the Sb₂Te₃ (ST) material has a face-centered cubic (Fcc) phase which contains a high concentration of vacancies at low temperature. Due to the poor amorphous thermal stability of ST, the as-deposited film obtained by physical vapor deposition is crystalline (Fcc phase). Therefore, we proposed a vacancy control mechanism, using inert gas Ar to ion implantation of as-deposited ST films, redistributing vacancies in the as-deposited ST films. Through different doses of Ar ion implantation, we obtain amorphous ST materials with different resistivity. We find that after the injection dose reached 1 × 10¹⁶ cm^-2, the effect of continued increase in the implantation dose on the resistivity of the thin film is negligible. After ion implantation, the transition temperature of the metastable Fcc phase to the hexagonal phase (Hex) is increased, which is beneficial to improve the power consumption and endurance of the device. The ST which is injected with a dose of 1 × 10¹⁶ cm⁻² Ar ion based phase-change memory cell can perform erasing operation in 100 ns, showing low power consumption potential. Our work provides a new idea and method for the application of future defect control in phase-change memory research.

Abstract: Proton beam writing was carried out into high purity semi-insulating 4H-SiC bulk substrates. Luminescent defects created in the SiC by proton beam writing using 1.7 MeV-proton micro beams were investigated at room temperature using confocal laser scanning microscope. As a result, photoluminescence peak around 900 nm associated with silicon vacancy was observed for the irradiated SiC without post implantation process such as annealing. The overall depth profile of photon counts detected from irradiated areas is in good agreement with simulated vacancy depth profile. This suggests that silicon vacancy can be applied to ion tracking detector. In addition, since silicon vacancy is known as single photon source of which spins can be controlled at RT, PBW is expected to be a useful tool to fabricate spin qubits.

Abstract: The purpose of this work is to consider the basic concepts on the present state of understanding of photocatalytic energy conversion using oxide semiconductors. This work also considers the approaches in derivation of theoretical models that allow explanation of the effect of properties on the performance of oxide-based photocatalysts in photocatalytic water oxidation. In this work we show that the performance of photocatalytic systems must be considered in terms of a range of the key performance-related properties (KPPs) that, in addition to the band gap, include the concentration of surface active sites, charge transport and Fermi level. Taking into account that all these KPPs are related to defect disorder, defect engineering may be applied in processing oxide semiconductors with optimal properties that are required to exhibit maximised performance in solar-to-chemical energy conversion.

Abstract: The evolution of Fe-related defects is simulated for di erent P di usion gettering (PDG) processes which are applied during silicon solar cell processing. It is shown that the introduction of an extended PDG is bene cial for some as-grown Si materials but not essential for all of them. For mc-Si wafers with an as-grown Fe concentration 14 cm³, a good reduction of the Fe_i concentration and increase of the electron lifetime is achieved during standard PDG. For mc-Si wafers with a higher as-grown Fe concentration the introduction of defect engineering tools into the solar cell process seems to be advantageous. From comparison of standard PDG with extended PDG it is concluded that the latter leads to a stronger reduction of highly recombination active Fe_i atoms due to an enhanced segregation gettering e ect. For an as-grown Fe concentration between 10¹⁴ cm³ and 10¹⁵ cm³, this enhanced Fe_i reduction results in an appreciable increase in the electron lifetime. However, for an as-grown Fe concentration >10¹⁵ cm³, the PDG process needs to be optimized in order to reduce the total Fe concentration within the wafer as the electron lifetime after extended PDG keeps being limited by recombination at precipitated Fe.

Abstract: A review is given of what kind technological aspects were used for realizing the defect engineering in semiconductor layers or crystals. The possibilities to change the free carrier capture are presented. The effect of Fermi level pinning at the surface levels allow to avoid the influence of barriers on the photoconductivity as well as to increase a role of recombination in the inter-crystalline region. The isovalent doping or the creation of the clusters allows transforming the defect distribution in the crystal bulk. The detector structure using the high electric field can introduce the recombination in at the contacts therefore allow diminishing a role of carrier capture in the bulk of structure. The cluster generation allows to increase the capture rate in the definite volume by a proton irradiation. The experience of different technologies for Si, GaAs, PbS, CdSe are presented.

Abstract: This paper reviews the physics and the potential application of ion-implanted vacancies for high-performance B-doped ultra-shallow junctions. By treatment of silicon films with vacancygenerating implants prior to boron implantation, electrically active boron concentrations approaching 1021 cm-3 can be achieved by Rapid Thermal Annealing at low temperatures, without the use of preamorphisation. Source/drain (S/D) junctions formed by advanced vacancy engineering implants (VEI) are activated far above solubility. Furthermore, in the case of appropriately engineered thin silicon films, this activation is stable with respect to deactivation and the doping profile is practically diffusionless. Sheet resistance Rs is predicted to stay almost constant with decreasing junction depth Xj, thus potentially outperforming other S/D engineering approaches at the ‘32 nm node’ and beyond.

Abstract: SIMOX (Separation-by-Implantation-of-Oxygen) is an established technique to fabricate silicon-on-insulator (SOI) structures by oxygen ion implantation into silicon. The main problem of SIMOX is the very high oxygen ion fluence and the related defects. It is demonstrated that vacancy defects promote and localize the oxide growth. The crucial point is to control the distribution of vacancies. Oxygen implantation generates excess vacancies around RP/2 which act as trapping sites for oxide growth outside the region at the maximum concentration of oxygen at RP. The introduction of a narrow cavity layer by He implantation and subsequent annealing is shown to be a promising technique of defect engineering. The additional He implant does not initiate oxide growth in the top-Si layer of SOI.

Abstract: The changes in microstructure and defect structure of two different semiconducting transition-metal silicides, ReSi1.75 and Ru2Si3 with ternary alloying of substitutional elements with a valence electron number different from that of the constituent metal have been investigated in order to see if the crystal and defect structures of these silicides and thereby their physical properties can be controlled through defect engineering according to the valence electron counting rule. The Si vacancy concentration and its arrangement can be successfully controlled in ReSi1.75 while the relative magnitude of the metal and silicon subcell dimensions in the chimney-ladder structures can be successfully controlled in Ru2Si3.

Abstract: Laser scattering tomography (LST) and band-to-band photoluminescence (PL) are applied for supporting a MEMS process optimization. Process wafers are based on magnetic CZ grown silicon material. LST allows the characterization of number-size distributions of oxygen precipitates in various stages of the process flow. Precipitation is shown to be affected by the design of high-temperature anneal post initial oxidation. PL gives useful information on relative concentration level and radial distribution of recombination centers within process wafers. The initial oxidation leads to significant reduction of recombination centers. The combined LST/PL information enables valuable conclusions towards process optimization.