Defect-Related White-Light Emission from ZnO in an n-Mg0.2Zn0.8O/n-ZnO/SiOx Heterostructure on n-Si

An n-Mg_0.2Zn_0.8O/n-ZnO/SiO _x (x < 2) heterostructure has been fabricated on n-Si by sputtering and electron-beam evaporation. The device showed nonrectifying behavior, and emitted strong white light under reverse bias with positive voltages applied to n-Si. The white-light electroluminescence (EL) is believed to result from electron–hole recombination at defect levels of ZnO. The EL mechanism has been tentatively explained in terms of the energy band structure of the device under forward and reverse bias.     

Electron correlation effects on polarons recombination in coupled polymer chains

The recombination dynamics of singlet and triplet oppositely charged polarons under the influence of electron–electron (e–e) interactions in coupled polymer chains are investigated using a multi-configurational time-dependent Hartree–Fock (MCTDHF) method. During recombination processes, singlet and triplet intrachain excitons are important products. By calculating the yields of the singlet and triplet intrachain excitons as a function of the on-site and long-range e–e interactions, it is found that the yields of the singlet and triplet intrachain excitons both decrease with increasing on-site e–e interactions. On the other hand, as the long-range e–e interactions increase, the yields of singlet intrachain excitons initially increase and then maintain a constant value, while the yields of the triplet intrachain excitons decrease. Our results show that the long-range e–e interaction is of fundamental importance and improves the luminescence efficiency in coupled polymer chains. Finally, the influence of the polymer chain length on the yields of singlet and triplet intrachain excitons is discussed.     

Electron irradiation induced recombination centers in silicon-minority carrier lifetime control

Recombination centers introduced in silicon p⁺-n-n⁺structures by irradiation with 2-MeV electrons are studied by measuring minority carrier lifetime and annealing kinetics. The approximate location of these recombination centers in the forbidden gap and their densities are obtained by the thermally stimulated current method. The results identify one defect as a divacancy with an energy level of Ev+ 0.26 eV. Possible identities of other deep levels are discussed. The technique of minority carrier lifetime control by electron irradiation has been developed into a reliable manufacturing process for power devices.     

Excitation of hypersound in n-GaN films

The aim of this paper is the analysis of hypersound excitation in GaN films. Simulation of process is presented for a case of a thin film geometry on a non-piezoelectric substrate. The frequency range considered is from 50 GHz up to 200 GHz. The excitation is due to coupling with space charge waves (SCWs) in GaN film. The amplification of SCWs is related with negative differential conductivity in GaN films. Possible spatial increments are obtained. The amplified SCWs can excite hypersonic waves at the same frequency due to piezoeffect and deformation potential mechanisms. The first effect is stronger and causes an effective resonant excitation of hypersonic waves in the case of full mechanic contact of GaN film and non-piezoelectric substrate.     

Metal/n-GaP Schottky barrier heights

A systematic study, which aims to extend the existing metal/n-Gap Schottky barrier height data, is made. Schottky diodes of various barriers, which included Pt/n-GaP, Au/n-GaP, Ni/n-GaP, Mo/n-Gap, Al/n-GaP, Cr/n-GaP, Ag/n-GaP and Cu/n-GaP, were fabricated and their I-V and C-V characteristics were measured. The derived barrier height values for Au, Cr, and Cu agree with the existing data. The derived I-V and C-V barrier height data on Ni, Mo and Ag extend the present barrier height data for n-type GaP. The C-V barrier height values are plotted vs work function of metals and a straight line relationship is obtained.     

The effect of single-phonon and plasmon recombination on the lifetime in n-Hg1−xCdxTe with magnetically tuned bandgap

Theoretical investigations have predicted a great enhancement of electron-hole recombinations by adjusting the bandgap of narrow-gap semiconductors to the energy of elementary excitation in solids such as phonons or plasmons. Such an enhancement of the recombination rate of excess carriers is very important in constructing far-I.R. devices and might be used to generate high densities of LO-phonons and plasmons. We report experimental evidence of the influence of these recombination channels on the photoconductivity and the excess carrier lifetime in semimetallic n-Hg_1−xCd_xTe alloys, whose induced bandgap is magnetically tuned through the relevant energies of the elementary excitations. Both from a comparison of theoretically estimated lifetimes with Auger lifetimes and from experimental observations the new recombination channels prove to be very efficient and dominate the behaviour near their resonance with the band-gap.     

n-Channel AlSb/GaSb modulation-doped field-effect transistors

We report the first fabrication of a GaSb n-channel modulation-doped field-effect transistor (MODFET) grown by molecular beam epitaxy. The modulation-doped structure exhibits a room temperature Hall mobility of 3140 cm² V⁻¹ s⁻¹ and 77 K value of 16000 cm² V⁻¹ s⁻¹, with corresponding sheet carrier densities of 1.3 × 10¹² cm⁻² and 1.2 × 10¹² cm⁻². Devices with 1 μm gate length yield transconductances of 180 mS mm⁻¹ and output of 5 mS mm⁻¹ at 85 K. The device characteristics indicate that electron transport in the channel occurs primarily via the L-valley of GaSb above 85 K. The effective electron saturation velocity is estimated to be 0.9 × 10⁷ cm s⁻¹. Calculations show that a complementary circuit consisting of GaSb n- and p-channel MODFETs can provide at least two times improvement in performance over AlGaAs/GaAs complementary circuits.     

Reliability comparison of an n cascade system with the addition of an n strength system

In the present paper we are comparing the reliability of two models: (i) the cascade system and (ii) the system having n strengths on a single stress. In both the cases the system has n strengths and a single stress. In the first case n strengths are cascaded and for each attack the stress is decreased. Whereas in the second case n strengths act in combination on the stress component. From the results obtained we can observe that when the attenuation factor is less than 0.5 the cascade model is more reliable, otherwise the second one is more reliable. Hence we infer that, at each attack, if the stress decreases the cascade model is more reliable.     

Reliability of single strength under n-stresses

In this paper we have considered the reliability of a system when n-stresses acted on a single strength component with probability distributions that were exponential, normal and gamma. We infer that when n-stresses act on a single strength component with an exponential distribution, the component has the same reliability as single stress and strength components which are connected in series, whereas normal and gamma distributions do not follow this rule.     

Approximate analysis of n-unit cold-standby systems

In this paper, a n-unit cold-standby system with a single repair facility is analysed using two approximate methods namely, cutting and clustering the state space. It has been assumed that the failure rate is constant and the repair time is arbitrarily distributed. A mathematical model is developed using semi-regenerative phenomena and systems of convolution integral equations satisfied by various state probabilities corresponding to different initial conditions are obtained. Explicit expressions for the expected number of failures and expected number of repair completions in an interval [0, t] are obtained. An iterative numerical method is used to solve the systems of integral equations obtained and a comparative study has been carried out between exact and approximate solutions.     

Theory of switching phenomena in metal/semi-insulator/n-p silicon devices

The theory of switching is presented for a structure consisting of a p⁺-n junction and a metal electrode separated from the N-section of the p⁺-n junction by a semi-insulating (leaky) layer.

When a negative bias is applied to the electrode, the section of the n-layer under the electrode goes into deep depletion. In this mode, the current through the device is limited by generation in the deeply depleted region. This is the high-impedance or OFF state of the device.

At a sufficiently high voltage, the switching voltage, V_s, the p⁺-n junction is turned on by either avalanching in the n-layer or by the deep-depletion region extending through to the p⁺-n region (punch-through). When the junction turns on, the n-section goes from deep-depletion towards inversion. Thus, the voltage across the device decreaseswith a concomitant increase in the current through the device. This is the switching mode. The switching voltage may be tailored by varying the doping and/or width of the n-section.

Following switching, the device comes into the steady-state when the current through the insulating layer is equal to the current flowing across the p⁺-n junction. The I-V characteristic of this highly conducting (ON state) mode is determined principally by the I-V characteristic of the semi-insulating film. By suitable choice of material this portion of the characteristic can approach zero dynamic impedance, i.e. a near-vertical characteristic, characterized by a low holding voltage. Capacitance and switching characteristics of the device are also discussed.     

HOT-CARRIER RELIABILITY IN n-MOSFETs USED AS PASS-TRANSISTORS

AC stressing is investigated to determine the hot-carrier reliability in a 0.5 μm CMOS technology and is interpreted by a quasi-static model based on distinct damage mechanisms. The hot-carrier dependence of n-MOSFETs operating in pass-transistor configurations is carefully studied as a function of the propagation time and geometry. It is shown that device degradation may exhibit in some cases a strong dependence on the propagation time and clearly differs from the simple case of inverter operation.     

Characteristics of n-CuInSe2/Au Schottky diodes

The n-CuInSe₂/Au point-contact Schottky diode was studied using current-voltage and capacitance-voltage measurements. Various important physical parameters of these diodes were derived from both measurements, and these values are comparable with the results reported on planar Schottky diodes.     

Experimental studies of switching in metal semi-insulating n-p silicon devices

The switching properties of silicon structures comprising a p⁺-n junction and a metal electrode separated from the n-section of the p⁺-n junction by a semi-insulating (leaky) layer are presented. Two basic types of structure were studied: devices with relatively light doped n-sections, and those with relatively heavily doped sections.

The switching voltage of the first group was found to be proportional to the product of the doping density, N_d and the square of the width of the n-section, and to be only very weakly temperature-dependent. The capacitance-voltage relationship of the device in the high-impedance mode was found to be of the form C⁻¹ ∞ V^1/2, and these measurements established that switching occurred just as the depletion region of the n-section under the gate electrode reached through to the p⁺-n junction. It was thus established that these devices were operating in the punch-through mode.

In the second group of devices, the doping density of the n-section was increased by diffusing an n-well into the section. The switching properties were found to be quite different from the punch-through devices. The switching voltage was found to be independent of the width of the n-section and proportional to N_d^−3/4. Capacitance measurements also showed that the depletion region in the n-section under the oxide at switching, varied with the doping concentration, and was substantially less than the width of the n-layer. It was thus concluded that switching in these devices was of the avalanche-mode type.     

Deep centers introduced by argon ion bombardment in n-type silicon

Platinum-silicon Schottky diodes on epitaxial layers have been subjected to argon ion bombardment, prior to metal evaporation, with doses in the 10¹⁴ ions/cm² range and with energies between 1 and 3.5 KeV. By transient capacitance technique four electron traps have been found. The oxygen-vacancy pair (O-V) located at 0.17 eV below the conduction band, the double negatively charged divacancy (V-V⁼) at 0.23 eV and the phosphorous-vacancy pair (P-V) at 0.44 eV are observed. One more unknown level at 0.36 eV which could be oxygen-related is also found.     

Numerical simulation of temperature-dependent minority-hole transport in n silicon emitters

A one-dimensional numerical computer simulation of minority-hole transport in heavily doped n⁺ silicon emitters is developed accounting for significant temperature dependences. The model includes the most recent insights regarding heavy-doping effects, which indeed facilitate the accounting for the temperature dependences. Measurements of base current in polysilicon-contacted n⁺pn transistors over a wide temperature range, carefully interpreted by accounting for unavoidable device/ambient temperature discrepancies, support the model and demonstrate its utility, for example in characterizing the electrical properties of the polysilicon emitter contact.     

Determination of transport parameters for InP device simulations in nn structures

Phenomenological transport parameters in n-InP are derived from large scale, ensemble Monte Carlo particle simulations. These parameters are required in efficient numerical methods used to solve “hydrodynamic-like” transport formulations which govern various physical models of bulk, unipolar InP devices. For an equivalent single-valley conduction band, a set of transport parameters in n-InP at 300 K is calculated from the Monte Carlo data. An example of the use of these parameters in a numerical simulation code is provided.     

Current reversals in p−n−p transistors

p−n−p silicon bipolar junction transistors (BJTs) have received a greater attention recently in light of the emerging dilemma of performance and power requirements for bipolar VLSI. The current reversal phenomena due to the avalanche breakdown have been the focus of the study of advanced Si p−n−p BJTs in the past. However, a thorough study of current reversals in p−n−p transistors has not been presented yet. In this paper, we study the base and collector current reversals in the inverse mode and their associated physical mechanisms. The collector and base current reversals have been found when the device is operated with or without avalanche effect. Physical mechanisms have been proposed to interpret these phenomena.