Recombination measurement of n-type heavily doped layer in high/lowsilicon junctions

The hole lifetime within a heavily doped n⁺ region has been determined using a measurement technique which evaluates the effective recombination velocity of n-n⁺ interfaces. The recombination model of a high/low junction is reviewed. The experiment is described. The measurement results are presented and discussed. Measurements of n⁺ layers of different types, like substrates, implanted buried layers, and diffused layers, suggest that the minority-carrier lifetime of such regions can be strongly degraded by the device fabrication processes. Results are consistent with the Shockley-Reed-Hall (SRH) lifetime value, which is two orders of magnitude lower than previously published values for bulk material     

Measurement of hole mobility in heavily doped n-type silicon

Accurate measurements of the mobility (and diffusion coefficient) of minority-carrier holes in Si:P with doping in the 10¹⁹cm^-3range have been done. The technique employed the measurement of diffusion length by means of lateral bipolar transistors of varied base widths, and the measurement of minority-carrier lifetime on the same wafers from the time decay of luminescence radiation after excitation with a short laser pulse. Minority-carrier hole mobility is found to be about a factor of two higher than the mobility of holes as majority carriers in p-type Si of identical doping levels.     

Novel method for extraction of hole transport parameters in heavily doped n-type emitter

A novel method is reported for the extraction of the hole transport parameters from the emitter of an n/sup +/pn bipolar transistor. The parameters are decoupled with a reliable algorithm based on the numerical solution of the transport equations. Accurate modelling of the optical spectral response of the base current has been achieved.<>     

A chromium-free etchant for delineation of defects in heavily doped n-type silicon wafers

Delineation of defects in the heavily doped n-type Czochralski silicon wafers by preferential etching is an issue not having been essentially solved. Herein, a chromium-free etchant based on HNO₃–HF–H₂O system, with an optimum volume ratio of V_HNO3%:V_HF%:V_H2O%=20%:45%:35%, has been developed. It can reveal well the defects such as dislocation and oxygen precipitation-induced bulk microdefects (BMDs) in the heavily doped n-type silicon wafers with resistivities even lower than 1 mΩ cm. Moreover, this etchant is appropriate to delineate the defects on (1 1 1), (1 1 0) or (1 0 0) surface of silicon crystal. Furthermore, the density of oxygen precipitation-induced BMDs in the heavily doped n-type silicon wafers derived from the preferential etching using this newly developed etchant correlates well with that derived from scanning infrared microscopy (SIRM) within its detection limit.     

Transport equations for the analysis of heavily doped semiconductor devices

Transport equations for use in analyzing heavily doped semiconductor devices are considered. These transport equations describe the effects of the nonuniform band structure and the influence of Fermi-Dirac statistics, which are important in heavily doped semiconductors. Previous workers [1, 2] have derived transport equations in terms of the nonuniform band structure. These equations, however, are not convenient for use in semiconductor device analysis because the band structure of heavily doped semiconductors is not well known. In this paper, the transport equations of Marshak and van Vliet [1, 3] are recast into a simple, Boltzmann-like form in which the effects associated with the nonuniform band structure and degenerate carrier concentrations are described by two parameters, the effective gap shrinkage, Δ_G, and the effective asymmetry factor, γ. The experimental determination of both of these parameters is also discussed. Finally, Adler's contention [4], that some important features of semiconductor device operation can be modeled accurately by using an electrically measured Δ_G with an arbitrarily chosen γ, is considered. The validity of this procedure, under certain simplifying assumptions, is established.     

Measurement of steady-state minority-carrier transport parameters in heavily doped n-type silicon

The relevant hole transport and recombination parameters in heavily doped n-type silicon under steady state are the hole diffusion length and the product of the hole diffusion coefficient times the hole equilibrium concentration. These parameters have measured in phosphorus-doped silicon grown by epitaxy throughout nearly two orders of magnitude of doping level. Both parameters are found to be strong functions of donor concentration. The equilibrium hole concentration can be deduced from the measurements. A rigid shrinkage of the forbidden gap appears as the dominant heavy doping mechanism in phosphorus-doped silicon.     

交叉杆结构忆阻器件的研究进展

忆阻器被认为是除电容器、电感器、电阻器之外的第四种无源器件,具有器件结构简单、操作速度快、功耗小等优点,是具有电阻记忆特性的非易失性的电阻元件。而交叉杆结构忆阻器件作为忆阻器的一种结构,由于其较之其他结构的忆阻器具有结构简单、集成度高、容错性和并行性优良等特性,受到了外界广泛的关注及研究。文章综述了近年来交叉杆忆阻器的兴起和发展现状,阐述了以交叉杆结构为基础的各类忆阻器的制备及应用。     

Multilevel characteristics for bipolar resistive random access memory based on hafnium doped SiO2 switching layer

We fabricated TiN/Hf:SiO₂/Pt memory cell with the small size of 1×1 um² by lithography and sputtering technology, which demonstrated excellent bipolar resistive switching (RS) characteristics. The device presents good endurance and outstanding uniformity. The coefficient of variation of V_set, V_reset, R_on and R_off were found to be 5.05%, 4.78%, 4.18%, and 15.78%, respectively. For the device with hafnium doped SiO₂ switching layer, multilevel storage capability can be successfully obtained by varying either the stop voltage or the compliance current in the SET process. In addition, the impact of forming current on the RS properties was studied. We found that the ratio of On/Off current for the device increased with the decrease of the forming current, which would be beneficial for the design of low power device. Possible RS mechanisms aiming to explain the impact of forming current on the RS characteristics and multilevel storage were also deduced.     

An etchant for delineation of flow pattern defects in heavily doped p-type silicon wafers

Secco etchant is conventionally used for delineation of flow pattern defects (FPDs) in lightly-doped Czochralski (Cz) silicon wafers. However, the FPDs in heavily doped p-type silicon wafers cannot be well delineated by Secco etchant. Herein, an etchant based on the CrO₃HFH₂O system, with an optimized volume ratio of V(CrO₃):V(HF)=2:3, where the concentration of CrO₃ is 0.25–0.35 M, has been developed for delineation of FPDs with well-defined morphologies for the heavily boron (B)-doped p-type silicon wafers.     

Unipolar resistive switching of Au+-implanted ZrO2 films

The resistive switching characteristics of Au+-implanted ZrO2 films are investigated.The Au/Cr/Au+-implanted-ZrO2/n+-Si sandwiched structure exhibits reproducible unipolar resistive switching behavior.After 200 write-read-erase-read cycles,the resistance ratio between the high and low resistance states is more than 180 at a readout bias of 0.7 V. Additionally,the Au/Cr/Au+-implanted-ZrO2/n+-Si structure shows good retention characteristics and nearly 100% device yield.The unipolar resistive switching behavior is due to changes in the film conductivity related to the formation and rupture of conducting filamentary paths,which consist of implanted Auions.     

金离子注入二氧化锆薄膜的单极电阻转变特性研究

The resistive switching characteristics of Au＋-implanted ZrO2 films are investigated. The Au/Cr/Au＋ -implanted-ZrO2/n＋-Si sandwiched structure exhibits reproducible unipolar resistive switching behavior. After 200 write-read-erase-read cycles, the resistance ratio between the high and low resistance states is more than 180 at a readout bias of 0.7 V. Additionally, the Au/Cr/Au＋-implanted-ZrO2/n＋-Si structure shows good retention characteristics and nearly 100% device yield. The unipolar resistive switching behavior is due to changes in the film conductivity related to the formation and rupture of conducting filamentary paths, which consist of implanted Au ions.     

Determination of boron concentration in heavily doped p-type Si1−xGex/Si heterostructure by infrared ellipsometric spectroscopy

Si_1−xGe_x/Si heterostructures play a primary role in the Si-based fast electronics developments of today. In this work, we will present the experimental results of infrared spectroscopic ellipsometry (IRSE) for structural determination of the boron heavily doped SiGe/Si sample grown by ultra-high vacuum chemical vapor deposition (UHVCVD) (the Ge atomic percent, the thickness of SiGe film and boron concentration). Especially, the principle of boron concentration in p-type SiGe film layer determined by IRSE was elucidated in detail. In addition, in order to corroborate the validity of IRSE for determining dopant concentration, secondary ion mass spectroscopy (SIMS) experiment has also been carried out. The close experimental agreement between IRSE and SIMS demonstrate that IRSE as a contactless, and non-destructive technology can be used in-line tools in production used for measuring the Ge content, the thickness of SiGe layer and boron concentration in p-type dopant SiGe/Si heterostructure, which often used the base layer of SiGe hetero-junction bipolar transistor (HBT) devices.     

Electrical band-gap narrowing in n- and p-type heavily doped silicon at 300 K

Based on previous results band-gap narrowing in heavily doped silicon at 300 K is investigated and expressed in terms of impurity size-and-doping effects. The results obtained for n- and p-type heavily doped silicon are compared with other theories and experiments.     

Switching properties of highly doped Gunn devices in resistive circuits

The switching behaviour of Gunn devices in the doping range between 7 × 10¹⁴ cm^?3 and 5 × 10¹⁵ cm^?3 acting in resistive circuits is investigated by numerical methods. Carrier transport equations including diffusion are solved for the device in combination with external circuit equations. The switching time is below 100 psec down to less than 10 psec depending on load and doping. The current pulse amplitude is about 40% of the peak current.     

The electrical characteristics of Sn/methyl-red/p-type Si/Al contacts

The junction characteristics of the organic compound methyl-red film (2-[4-(dimethylamino)phenylazo]benzoic acid) on a p-type Si substrate have been studied. The current-voltage characteristics of the device have rectifying behavior with a potential barrier formed at the interface. The barrier height and ideality factor values of 0.73 eV and 3.22 for the structure have been obtained from the forward bias current-voltage (I-V) characteristics. The interface state energy distribution and their relaxation time have ranged from 1.68 × 10¹² cm⁻² eV⁻¹ and 1.68 × 10⁻³ s in (0.73-E_v) eV to 1.80 × 10¹² cm⁻² eV⁻¹ and 5.29 × 10⁻⁵ s in (0.43-E_v) eV, respectively, from the forward bias capacitance-frequency and conductance-frequency characteristics. Furthermore, the relaxation time of the interface states shows an exponential rise with bias from (0.43-E_v) eV towards (0.73-E_v) eV.     

Growth and characteristics of p-type doped GaAs nanowire

The growth of p-type GaAs nanowires (NWs) on GaAs (111) B substrates by metal-organic chemical vapor deposition (MOCVD) has been systematically investigated as a function of diethyl zinc (DEZn) flow.The growth rate of GaAs NWs was slightly improved by Zn-doping and kink is observed under high DEZn flow.In addition,the I-V curves of GaAs NWs has been measured and the p-type dope concentration under the Ⅱ/Ⅲ ratio of 0.013 and 0.038 approximated to 1019-1020 cm-3.     

Bipolar switching characteristics of low-power Geo resistive memory

We reported an ultra low-power resistive random access memory (RRAM) combining a low-cost Ni electrode and covalent-bond GeO_x dielectric. This cost-effective Ni/GeO_x/TaN RRAM device has very small set power of 2 μW, ultra-low reset power of 130 pW, greater than 1 order of magnitude resistance window, and stable retention at 85 °C. The current flow at low-resistance state is governed by Poole-Frenkel conduction with electrons hopping via defect traps, which is quite different from the filament conduction in metal-oxide RRAM.     

Low voltage bipolar resistive switching in self-assembled PVDF nanodot network in capacitor like structures on Au/Cr/Si with Hg as a top electrode

In this letter, resistive switching phenomena in self-assembled nanodot network of Polyvinylidene fluoride (PVDF) polymer in a capacitor geometry of Hg/PVDF/Au/Cr/Si is investigated. A stable & bipolar resistive switching with a set voltage ranging from 0.35 V to 0.9 V & reset voltage with a range of −0.08 V to −0.25 V is detected. A practical resistance ratio between HRS and LRS of 10–25 may have great potential in organic memories. Possible mechanism for the bipolar switching is discussed with the filament type conduction mechanism. Furthermore, the low voltage switching is elucidated with the high current density associated filament formation and it is explicated using the parallel resistor model.     

Effects of resistive switching in Au/FeO<Subscript>x</Subscript>/Pt structures

The dynamics of forming and resistive switching in Au/iron oxide/Pt structures based on magnetite (Fe₃O₄) is investigated. It has been revealed that these processes have an electrochemical nature and are accompanied by formation of low-resistance conductive filaments formed by inclusions of magnetite in the matrix of high-resistance maghemite (γ-Fe₂O₃). It has been found that the electric field stimulates reversible redox reactions in iron oxide. The direction and rate of these reactions are determined by the polarity and the amplitude of voltage pulses. The possibility of setting the resistance of the structure by changing the amplitude of the “record” voltage pulses opens prospects for the development of multilevel memory elements.