A comparison of majority- and minority-carrier silicon MIS solar cells

A systematic experimental investigation is reported of metal-SiO2-silicon (MIS) solar cells, as a function of SiO2thicknessd, in the useful range 8 Å <d< 20 Å. Both majority-carder (Au-SiO2- nSi) and minority-carrier (Al-SiO2-pSi) structures are studied and their performance compared for SiO2layers prepared under identical oxidation conditions and with identical silicon surface treatments. The short-circuit current densities are observed to be suppressed by tunneling through the SiO2layers ford gsim 17Å, whereas fill factors begin to decrease at even smaller values of d. The optimum effective AM1 conversion efficiencies for the majority-carrier cells are 9-10 percent for 10 Å ≲d≲ 14 Å, and for the minority-carrier cells are 11-12 percent ford simeq 10-11Å. These results are in agreement with theoretical calculations, also presented here, which take account of both electrostatic and dynamic effects of interface states, and of their dependence on bias voltage and illumination.     

The effects of small-amplitude potential changes on nonequilibrium minority-carrier charge distributions in MIS capacitors

In this work we examine the response of minority carriers in metal-insulator-semiconductor (MIS) capacitors to small-amplitude step excitation for times sufficiently short to preclude the attainment of equilibrium. The analysis, carried out in the depletion and weak inversion regimes, is shown to be consistent with previously described phenomenological arguments regarding the response in heavy inversion. In addition, the present analysis takes into account changes in minority carrier population produced by surface-state generation or other phenomena. The results are used to describe the response of the surface minority-carrier density to square-wave excitation in a surface-state-free structure.     

Electrical analysis of organic dye-based MIS Schottky contacts

In this work, we prepared metal/interlayer/semiconductor (MIS) diodes by coating of an organic film on p-Si substrate. Metal(Al)/interlayer(Orange GOG)/semiconductor(p-Si) MIS structure had a good rectifying behavior. By using the forward-bias I-V characteristics, the values of ideality factor (n) and barrier height (BH) for the Al/OG/p-Si MIS diode were obtained as 1.73 and 0.77 eV, respectively. It was seen that the BH value of 0.77 eV calculated for the Al/OG/p-Si MIS diode was significantly larger than the value of 0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the potential barrier of Al/p-Si diode was achieved by using thin interlayer of the OG organic material. This was attributed to the fact that the OG organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 2.79 × 10¹³ to 5.80 × 10¹² eV⁻¹ cm⁻².     

Measurement of minority-carrier lifetime in silicon at microwave frequencies using microstrip techniques

A method is described for measuring minority-carrier lifetime in semiconductor samples of any thicknes and dimensions (e.g. silicon is used in device fabrication). The semiconductor sample is used as the dielectric of a microstrip line sandwitched between a ground plane of electroplated gold (or other metal) and electroplateted strip conductor delineated using standard photoresist masking techniques.     

Modeling of small-signal minority-carrier transport in bipolardevices at arbitrary injection levels

A detailed analytical treatment of small-signal minority-carrier transport in quasi-neutral regions with position-dependent material parameters at arbitrary injection levels is presented. First, the small-signal minority-carrier transport equations are derived in a simple form which is amenable to analytical integration, thereby facilitating physical insight. Secondly, analytical solutions of the transport equations are derived by means of the integral series solution method. Next, it is shown that these solutions provide a mathematically sound basis for a systematic derivation of all nonquasi-static models hitherto presented in the literature for both the base and emitter regions of bipolar transistors. An important consequence of the above analysis is that the exact expression of all model parameters is obtained. These parameters include the conductance, transit time, charge partitioning factor and phase-shift factor. The dependence of these parameter on the most significant technological parameters and on the operating point is analyzed in detail     

New method for producing ideal metal-semiconductor ohmic contacts

A new understanding of ohmic-contact alloying in terms of liquid-epitaxy processes has led to improved contact fabrication by using a slow alloying cycle with an As overpressure chamber. A conveniently wide range of As pressures is possible when Ga is deposited together with the other metals.     

塑封互联MIS高可靠性封装及板级封装新技术

塑封互联MIS技术是一种高性能、高可靠性封装基板及板级嵌入式封装技术,其灵活的布线及特有的材料结构及工艺特点,结合MIS基板中铜布线超粗化等表面处理工艺,在电、热性能及可靠性方面相比现有BGA、QFN等封装凸显出显著的优势。基于MIS工艺的灵活性,目前在封装领域尤其在嵌入式封装、系统级封装等方面表现优异,已广泛应用于手机、工业控制、IOT等电子产品的射频类、电源管理类器件的封装中。文章对MIS技术主要工艺流程、技术特点、在各类封装中的应用、电热性能等进行了阐述。     

A fast extrapolation technique for measuring minority-carrier generation lifetime

The transient response of a pulsed MOS capacitor is used to calculate the minority-carrier generation lifetime. For Si substrate with a long lifetime, traditional approaches suffer from the inefficiency of long measurement times. An extrapolation technique presented here significantly reduces the measurement time while still maintaining good accuracy. This method applies to capacitors with constant bulk-generation rates. The linear correlation coefficient of the 1n W-t plot is monitored to ensure accuracy of the measurement technique.     

Experimental study of the minority-carrier transport at the polysilicon—monosilicon interface

This paper presents the results of an experimental study designed to explore both qualitatively and quantitatively the mechanism of the improved current gain in bipolar transistors with polysilicon emitter contacts. Polysilicon contacts were deposited and heat treated at different conditions. The electrical properties Were measured using p-n junction test structures that are much more sensitive to the contact properties than are bipolar transistors. A simple phenomenological model was used to correlate, the structural properties with electrical measurements. Possible transport mechanisms are examined and estimates are made about upper bounds on transport parameters in the principal regions of the devices. The main conclusion of this study is that the minority-carrier transport in the polycrystalline silicon is dominated by a highly disordered layer at the polysilicon-monosilicon interface characterized by very low minority-carrier mobility. The effective recombination velocity at the n⁺polysilicon-n⁺monosilicon interface was found to be a strong function of fabrication conditions. The results indicate that the recombination velocity can be much smaller than 10⁴cm/s.     

New techniques for the study of Gunn diode contacts

Measurements are reported which provide direct evidence of the relationship between the frequency-temperature behaviour of GaAs and InP Gunn diodes and the quality of their cathode contacts. The technique used consists of damaging the cathode contact in a controlled manner while monitoring the current-voltage characteristic and df/dT.These results are compared with computer simulations of I-V characteristics and RF performance using a model diode with a region of either reduced carrier concentration or reduced mobility immediately beneath the contact. Qualitative agreement is obtained between theory and experiment.Magnetoresistance measurements on diodes both before and after damage are analysed to show that the damaged contact region contains both reduced carrier concentration and reduced mobility. Computer simulation using an appropriate model predicts I-V characteristics in general agreement with experimental observations.     

Modeling of minority-carrier transport in semiconductor regionswith position-dependent material parameters at arbitrary injectionlevels

An analytical treatment of minority-carrier transport in bipolar transistors under arbitrary injection levels is presented. The analysis is not restricted to particular doping profiles and applies also to SiGe devices. As a first result, it is demonstrated that the minority-carrier transport equation is exactly soluble at high-injection (HI) levels, yielding closed-form expressions for the injected current, transit time, and sheet resistance. Contrary to the presently available formula which is recovered here as a particular case, our result reveals that the HI transit time is strongly affected by band-gap narrowing effects. It is also found that the transit time increase due to velocity saturation is more pronounced at HI levels than at low-injection (LI) levels. An analytical formulation for the collector current density, base transit time, and base sheet resistance, valid at any injection level, is then proposed. The analysis is based on the construction of approximate solutions of the transport equation. Finally, a simple expression for the effective electric field is derived, which allows one to more clearly study its variation with the injection level, and to easily take into account the electric field-dependence of the mobility     

Multiple Andreev reflection in hybrid AlGaAs/GaAs structures with superconducting NbN contacts

The conductivity of hybrid microstructures with superconducting contacts made of niobium nitride to a semiconductor with a two-dimensional electron gas in a AlGaAs/GaAs heterostructure has been investigated. Distinctive features of the behavior of the conductivity indicate the presence of multiple Andreev reflection at scattering centers in the normal region near the superconductor-semiconductor boundary. Fiz. Tekh. Poluprovodn. 33, 590–593 (May 1999)     

Statistical model for electromigration failure at aluminum contacts and terminals

The statistical model for electromigration failure in stripes developed by Attardo, Rutledge, and Jack has been extended to cover the cases of terminals and contacts to silicon. By the use of computer simulation techniques, a model was developed that relates the time-to-failure and the distribution of failures to the magnitude of the structural divergence occurring at the diffusion barrier. The model is then used to predict the dependence of contact or terminal reliability on grain size distribution, device geometry, and current crowding. In particular, the model predicts the previously unknown fact that for a constant grain size, a large standard deviation of the grain size at the contacts will retard electromigration and that the current density distribution at the contact does not affect mean time-to-failure.     

Wall reflection modelling for horn directional antenna at EHF

The effect of directional horn antenna radiation patterns is important to characterise an indoor radio channel. Instead of a single ray, the main possible rays of departure and arrival are considered according to the directional horn transmitter and receiver antenna radiation patterns using ray tracing. Computation results fit well with the measurements upon wall reflection at the EHF band.     

Determination of the minority-carrier lifetime in silicon ingots by photoconductivity relaxation measured at microwave frequencies

A new method for determining the bulk lifetime of minority carriers in single-crystal silicon ingots is proposed. A photoconductivity signal measured at a microwave frequency and normalized to its initial value is compared with the results of calculating the total number of excess charge carriers N(t)/N_st, where N_st corresponds to the quasi-steady-state photoconductance. The location of the point of intersection of the photoconductivity-relaxation curve and the dependence N(t=τ)/N_st determines the bulk lifetime τ=τ_v. The measurements were performed on silicon ingots with different resistivities grown by crucibleless zone melting and the Czochralski method. The experimental data obtained agree well with the results of calculation.     

New method for determining distribution of interface states in an MIS system

A general formula for the capacitance transient response in an MIS system was developed in order to apply the ICTS (isothermal capacitance transient spectroscopy) technique to an MIS diode. A new spectroscopic measurement method for determining the distribution of interface states is proposed and applied to an InAs MIS diode.     

An experimental technique for the study of non-avalanche charge injection or trapping in MIS structures

In the study of charge injection in the insulator-silicon system, variation of the electric field in the insulator, caused by charge trapping during a measurement, makes the interpretation and analysis of experimental data difficult.A measuring system and test device structure are described in which it is possible to monitor any change of the device threshold voltage and to adjust the applied gate voltage so as to maintain a constant electric field at the insulator-silicon interface.Experimental results will be presented which show the advantages stemming from this mode of operation.     

Exploiting diffusion currents at Ohmic contacts for trap characterization in organic semiconductors

Studying space-charge limited currents enables fundamental insight into the properties of charge carrier transport. However, in unipolar devices with Ohmic contacts, diffusion of charge carriers from the contacts into the intrinsic layer can dominate the current–voltage (J–V  ) characteristics, especially when the devices are thin as in organic electronic devices (∼$\sim$100 nm). Thus, the common approximation of drift-only trap-limited currents (J∼V^l+1$J\sim V^{l+1}$) caused by an exponential distribution of traps is not applicable for determination of the trap distribution. Here, we show by numerical drift–diffusion simulations of unipolar devices with p-doped injection layers (p–i–p devices), how diffusion currents affect the J–V power law depending on the intrinsic layer thickness for typical transport parameters of organic semiconductors. As the thickness dependence of the power law is characteristic of the trap distribution, the distribution can be determined from a simple variation of the device thickness.     

Current spreading at contacts to planar Gunn devices

The implications of current constriction at a planar contact to GaAs are inferred from the results of a simpler case (current flow to a small conducting cylinder). It is argued that a number of the pathological properties of Gunn diodes can be explained in terms of this mechanism.     

A new solution for minority-carrier injection into the emitter of a bipolar transistor

A new analytic solution for minority-carrier injection into the emitter of a bipolar transistor has been derived. Effects such as Shockley-Read-Hall (SRH) recombination, Auger recombination, bandgap narrowing, graded impurity profile, and position-dependent mobility have been included. A quantitative definition of "transparency" in an emitter is presented. Numerical results show the appearance of a minimum in injected minority-carrier current with respect to the impurity concentration at the surface. This minimum is due to the interaction of Auger recombination and the built-in electric field as impurity concentration is increased. The relative ease and speed necessary to obtain numerical results makes this method very useful for the design and optimization of transistors.