Papers by Keyword: Germanium

Abstract: The centers of bismuth (Bi) in silicon are being scrutinized as the defect qubits for mostly developed integrated electronics including its photonic component and we have applied the positron annihilation lifetime spectroscopy (PALS) to gain deeper insight into symmetry of the Bi impurity center whose configuration was modified by 15 MeV proton irradiation. It was revealed that hyperfine (hf) and super-hyperfine (shf) interactions of the nuclear and electron spin systems of the bismuth impurity center, ²⁰⁹Bi (J = 9/2), with the regular ²⁹Si (J = 1/2) atoms of silicon delay the essentially local event of emitting of a couple of annihilation gamma–quanta from within the crystal cell which comprises Bi impurity atom (J is the nuclear spin). This phenomenon is observed under increasing occupancy of Bi donor ground and excited states, in contrast to a profoundly enriched ²⁸Si (J = 0) material (so-called “semiconductor vacuum”) where content of ²⁹Si (J = 1/2) isotope was suppressed up to the value of ≈ 50 ppm. The many-body exciton-like states comprising a polyelectronic exciton {e⁻e⁺e⁻h} at Bi donor center are suggested for interpreting the data. The proton irradiation leads to acquiring by Bi impurity atom of an open volume ( V_op ) which is splitted in [V_op – Bi] complex. This defect possessing of D_3d symmetry dominates in the irradiated material. Being thermally stable up to ≈ 370 °C, [V_op – Bi] complex is annealed at ~ 470 – 500 °C. These data agree well with the results of ab intio cluster calculations performed on the basis of LDA-KKR formalism for exploring both the energy gain and symmetry of Bi–vacancy complex.

Abstract: Fluorinated chemistries can lead to severe corrosion damage towards silicon and germanium based materials when wafers have a significant amount of electrostatic charges. This corrosion is evidenced on both single wafer and batch tools. It can be prevented by the presence of enough light, and wafer charging can also be eradicated by photo emission with UV light.

Abstract: A systematic germanium (Ge) and vanadium (V) study on 4H-SiC epitaxial layers is presented. Electrical results of TLM structures which were fabricated on these layers revealed that highly-doped Ge and V-implanted layers showed extremely low specific contact resistivity, down to 2 x 10^-7 Ω.cm². Current flow in the conducting state of Schottky barrier diodes has been successfully suppressed in some implanted layers, with highly V doped samples showing current density values of approximately 1 x 10^-5 Acm^-2 at 10 V. DLTS spectra reveal the presence of germanium and vanadium centers in the respective samples as well as novel peaks which are likely related to the formation of a novel GeN center.

Abstract: In this work, germanium nanowires (GeNWs) were fabricated by galvanostatic electrodeposition using In nanoparticles from water solutions at different temperatures. It was found that in the temperature range from 10°C to 60°C there was no significant change in the structure of GeNWs, and the average diameter was about 40 nm. The growth time of GeNWs increases linearly with increasing temperature of the electrolyte solution. However, the structure of GeNW obtained at a solution temperature of 90°C has changed. It was shown that these GeNWs have a core-shell structure: the core is a crystalline Ge phase containing In atoms, and the shell is Ge oxides (hydroxides).

Abstract: During the last decade, silicon carbide (SiC) and its heterostructures with other semiconductors have gained a significant importance for wide range of electronics applications. These structures are highly suitable for high frequency and high power applications in extremely high temperature environments. SiC exists in more than 200 different polycrystalline forms, called polytypes. Among these 200 types, the most prominent polytypes with exceptional physical and electrical attributes are 3C-SiC, 4H-SiC and 6H-SiC. Heterostructures of these SiC polytypes with other conventional semiconductors (like Si, Ge) can give rise to interesting electronic characteristics. In this article, Germanium (Ge) has been used to make heterostructures with 3C-SiC and 4H-SiC using a novel technique called diffusion welding. Microscale and nanoscale simulations of nn-heterojunction of Ge/3C-SiC and Ge/4H-SiC have been done. Microscale devices have been simulated with a commercially available semiconductor device simulator tool called Silvaco TCAD. Whereas nanoscale devices have been simulated with QuantumWise Atomistix Toolkit (ATK) software package. Current-voltage (IV) curves of all simulated devices have been calculated and compared. In nanoscale device, the effects of defects on IV-characteristics due to non-ideal bonding (lattice misplacement) at heterojunction interface have been analyzed. Our simulation results reveal that the proposed heterostructure devices with diffusion welding of wafers are theoretically possible. These simulations are the preparations of our near future physical experiments targeted to fabricate SiC based heterostructure devices using diffusion bonding technique.

Abstract: The paper proposes analytical model for Gate-All-Around Metal Oxide Semiconductor Field Effect Transistor (GAA-MOSFET) for germanium channel including quantum mechanical effects. It is achieved by solving coupled Schrodinger-Poisson’s equation using variational approach. The proposed model takes quantum confinement effects to obtain charge centroid and inversion charge model. By using these models the quantum version of inversion layer capacitance, inversion charge distribution function and Drain current expressions are modelled and the performance evaluation of the developed model is compared with Silicon channel GAA-MOSFET. Analytically modelled expressions are verified by comparing the model with simulation results.

Abstract: The crystal structures of the binary compounds ZrAl₃ and HfAl₃ at 600°C belong to the structure type ZrAl₃ (Pearson symbol tI16, space group I4/mmm, a = 4.00930(11), c = 17.2718(7) Å for ZrAl₃ and a = 3.9849(3), c = 17.1443(15) Å for HfAl₃). Substitution of Ge atoms for Al atoms in ZrAl₃ and HfAl₃ led to the formation of the ternary compounds ZrAl_2.52(1)Ge_0.48(1) and HfAl_2.40(1)Ge_0.60(1), respectively, where the latter is probably part of a solid solution extending from the high-temperature modification of HfAl₃. The crystal structures belong to the tetragonal structure type ht-TiAl₃ (tI8, I4/mmm, a = 3.92395(11), c = 9.0476(4) Å for ZrAl_2.52Ge_0.48 and a = 3.9021(2), c = 8.9549(8) Å for HfAl_2.40Ge_0.60). The structure types ZrAl₃ and ht-TiAl₃ are both members of the family of close-packed structures.

Abstract: The crystal structure of the binary compound DyGa₃ at 600°C belongs to the structure type Ta (Rh_0.33Pd_0.67)₃ (Pearson symbol hP40, space group P6₃/mmc: a = 6.1617(3), c = 23.0365(18) Å). Progressive substitution of Ge atoms for Ga atoms in DyGa₃ at 600°C led to the formation of two ternary compounds: DyGa_2.92-2.52Ge_0.08-0.48 (structure type Mg₃In, hR48, R3m, a = 6.1707(3)-6.22374(10), c = 27.7297(15)-28.1185(5) Å) and DyGa_2.32-2.20Ge_0.68-0.80 (PuAl₃, hP24, P6₃/mmc, a = 6.0970(3)-6.1091(6), c = 14.3153(8)-14.3528(14) Å). Both structure types belong to the family of close-packed structures, and the increase of the Ge content in the system DyGa_3-xGe_x is accompanied by a decrease of the hexagonality of the close-packing. Both ternary compounds exhibit metallic type of electrical conductivity.

Abstract: We report on the (electro) chemical etching behavior, surface morphology and composition of n-type Ge (100) in acidic halide solutions using various analytical and spectroscopic techniques. The use of an integrated (electro) chemical etching chamber connected to X-ray photoelectron spectroscopy instrument to exclude the effect of oxygen from atmosphere is highlighted.

Abstract: Elemental semiconductors play an important role in high-technology equipment used in industry and everyday life. The first transistors were made in the 1950ies of germanium. Later silicon took over because its electronic band-gap is larger. Nowadays, germanium is the base material mainly for γ-radiation detectors. Silicon is the most important semiconductor for the fabrication of solid-state electronic devices (memory chips, processors chips, ...) in computers, cellphones, smartphones. Silicon is also important for photovoltaic devices of energy production.Diffusion is a key process in the fabrication of semiconductor devices. This chapter deals with diffusion and point defects in silicon and germanium. It aims at making the reader familiar with the present understanding rather than painstakingly presenting all diffusion data available a good deal of which may be found in a data collection by Stolwijk and Bracht [1], in the author’s textbook [2], and in recent review papers by Bracht [3, 4]. We mainly review self-diffusion, diffusion of doping elements, oxygen diffusion, and diffusion modes of hybrid foreign elements in elemental semiconductors.Self-diffusion in elemental semiconductors is a very slow process compared to metals. One of the reasons is that the equilibrium concentrations of vacancies and self-interstitials are low. In contrast to metals, point defects in semiconductors exist in neutral and in charged states. The concentrations of charged point defects are therefore affected by doping [2 - 4].