Collector Voltage Research Articles

Hot-electron electroluminescence in AlGaAs/GaAs heterojunction bipolar transistors

When biased in the active region at high collector voltages, AlGaAs/GaAs single heterojunction bipolar transistors have been observed to emit light in the 1.1–2.5 eV energy range. The spectral distribution of the emitted radiation results from the superimposition of (i) two peaks at about 1.4 and 2.1 eV, due to band-to-band recombination of cold electrons and holes, and (ii) a nearly exponential tail due to hot-electron-induced electroluminescence, whose intensity depends on reverse collector-base voltage. Moreover, a linear correlation has been found between the intensity of the hot-electron-induced electroluminescence and the current generated by impact ionization.

Collector-assisted operation of micromachined field-emitter triodes

The field at the tip of a field emitter triode can be expressed by E= beta V/sub g/+/sub gamma /V/sub c/, where V/sub g/ and V/sub c/ the gate and collector voltages, respectively. For small gate diameters and tips below or in the plane of the gate and/or large tip-to-collector distances, /sub gamma /V/sub c/ >

Monte Carlo Study of Charge Injection Transistors (CHINTs)

Self-consistent Monte Carlo simulation of the characteristics of charge injection transistors (CHINTs), with special focus on the bias voltage and the channel length dependences of these characteristics, shows that the transconductance of CHINTs increases with increasing collector voltage until the leak current becomes extremely high. Simulation also reveals that the area associated with real-space transfer (RST) is about one-third of the channel, suggesting that CHINTs can operate faster than conventional metal-insulator-semiconductor field-effect transistors (MISFETs). We also investigated the number of electrons that transfer from each valley for two different band configurations and found that RST from the L-valley in GaAs dominates even though the energy level of the L-valley is greater than the heterobarrier height.

Ignition and extinguishing characteristics of Cs-Ba tacitron

The operation characteristics of the Cs-Ba tacitron as a switch are investigated experimentally in three modes: (a) breakdown mode; (b) I-V mode; and (c) current modulation mode. The switching frequency, grid potentials for ignition and extinguishing of discharge, and the Cs pressure and emission conditions (Ba pressure and emitter temperature) for stable current modulation are determined. The experimental data is also used to determine the off time required for successful ignition, and the effects of the aforementioned operation parameters on the ignition duty cycle threshold for stable modulation. Operation parameters measured include switching frequency up to 8 kHz, hold-off voltage up to 180 V, current densities in excess of 15 A/cm2, switch power density of 1 kW/cm2, and a switching efficiency in excess of 90% at collector voltages greater than 30 V. The voltage drop strongly depends on the Cs pressure and to a lesser extent on the emission conditions. Increasing the Cs pressure and/or the emission current lowers the voltage drop, however, for the same initial Cs pressure and emission conditions, the voltage drop in the I-V mode is usually lower than that during current modulation. As long as the discharge current is kept lower than the emission current, the voltage drop during stable current modulation could be as low as 3 V.

Millimeter-wave AlGaAs-GaAs HBT power operation

The AlGaAs-GaAs HBT has demonstrated good power performance up to 18 GHz. Although f/sub max/ is typically above 100 GHz, the power performance limitation and large signal operation at millimeter wave frequencies have not been studied. Power results from two HBT structures at 35 GHz are analyzed based on numerical simulation. The HBT demonstrated 8.5-dB linear power gain, 30% PAE with 7.8-dB gain and 7.5-V V/sub ce/ bias. The power density reaches 1.25 mW/ mu m/sup 2/. A shorter collector (0.4 mu m) is shown to be better suited for 35-GHz operation as a result of shorter collector transit time and smaller residual collector voltage. Improvement can be achieved by reducing the base and collector resistance, and the collector capacitance. >

Dielectric–base transistor using YBa2Cu3O7−x/NdGaO3/SrTiO3 heterostructures

This paper describes the fabrication and evaluation of dielectric-base transistors having high-Tc YBa2Cu3O7−x electrodes with NdGaO3 low-permittivity barriers on SrTiO3 high-permittivity substrates. The YBa2Cu3O7−x/NdGaO3/SrTiO3 heterostructures were made by laser ablation. Nb base electrodes were sputtered on the back of the SrTiO3 substrate. The device showed transistor characteristics with voltage and current gains exceeding unity at 4.2 K. The collector current density was about 10 A/cm2 at a collector voltage of 20 V, four orders of magnitude larger than that obtained for devices having no artificial barriers.

An AlSb–InAs–AlSb double-heterojunction P-n-P bipolar transistor

We report the experimental demonstration of AlSb–InAs P-n-P double-heterojunction bipolar transistors. The devices exhibited net current gain and supported a substantial collector voltage of VCE≳2.5 V. The device structure was grown by molecular-beam epitaxy on a (001)-oriented p+ GaAs substrate. The base thickness was 100 nm, with a degenerate n-type base doping level (Si) of 2×1018 cm−3. The p-type emitter and collector doping levels (Be) were 5×1016 cm−3. The collector currents obeyed a typical Gummel relation, with parameters close to those expected from theory, making allowance for the high degree of degeneracy and the nonparabolicity in the InAs base region. However, the base currents were still high, apparently due to extensive interface recombination via unknown defects at the InAs–AlSb emitter-base junction. The base currents could be described well by a Sah–Noyce–Shockley model, modified to account for the unusual abrupt staggered lineup heterojunction and the degeneracy on the InAs side.

Collector-induced field emission triode

By positioning the gate below the tip in a vacuum triode, field emission can be initiated by the collector voltage V/sub c/ and the emission current can be modulated by the gate voltage V/sub g/. Principle of operation is demonstrated for a single-tip,

High-speed InGaAs/InP composite collector bipolar transistors

The authors describe a composite collector bipolar transistor structure capable of high-speed and high breakdown voltage (BV/sub CEO/). The structure uses a composite collector of InGaAs and InP. f/sub T/=120 GHz at V/sub CE/=1.5 V at a current density of 77 kA/cm/sup 2/ were obtained. The breakdown voltage BV/sub CEO/ is greater than 5 V, and the output conductance is essentially independent of the collector voltage. Microwave transistors with an emitter size of 3*10 mu m/sup 2/ were fabricated by a self-aligned process. Microwave measurements were made from 100 MHz to 40 GHz as a function of the collector current and V/sub CE/. The authors have also fabricated and tested transimpedance amplifiers based on the composite collector transistors.

ADVANCED DEVICE MODELLING AT PHILIPS: THE CURRY PACKAGE

The package CURRY offers a wide range of built‐in facilities for 2D device modelling of a large variety of structures such as MOS, bipolar and charge coupled devices. These capabilities will be illustrated on the transport of a charge package in a charge coupled device and on the simulation of the ESD ( Electro‐Static Discharge) in an MOS transistor. The CURRY package can also be used as a high quality kernel to which the user may add his own extensions by adding small pieces of Fortran code. The flexibility of this setup will be shown in the computation of the threshold voltage of an MOS transistor, in the computation of the I‐V curve of a diode in avalanche breakdown and in the computation of the open collector voltage of a bipolar transistor.

A transistor model for numerical computation of forward-bias second-breakdown boundary

A two-dimensional bipolar power transistor model for numerical computation of the forward-bias, second-breakdown boundary is proposed. The model takes into account high-current-density effects such as the base widening (Kirk's) effect and avalanche injection. The numerically determined forward-bias safe operating area is in good agreement with the experimentally obtained area, especially at high collector currents and lower collector voltages. The model is also used to analyze the dynamics of the forward-bias second breakdown. The model is verified experimentally, and is suitable for a parametric study of forward-bias second breakdown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gold–silicon interface modification studies

We have performed ballistic electron emission microscopy measurements on the Au–Si system with and without controlled monolayer impurities at the interface. At moderate sample to scanning tunneling microscopy tip biases (&amp;lt;2.5 V) we have observed, and at high biases (&amp;gt;3 V) modified the local ballistic transmittance (BT), i.e. the scaling factor of the collector current versus voltage spectra, of the interface. Spatially, the modification typically consists of a region of decreased BT a few hundred Å in diameter surrounded by a ring of increased BT. No change in Schottky barrier height is found. A model is presented which describes the decrease in terms of Au–Si interdiffusion, and the enhancement in terms of a thinning of an impurity layer between the Au and Si; connections are made to observations of the unstressed system.

DC I-V characteristics of field emitter triodes

A simple model that is applicable to Spindt-type emitter triodes is presented. Experimentally, it has been observed that the gate current at zero collector voltage follows the same Fowler-Nordheim law as the collector current at high collector voltage, and that for low emission current densities, the sum of gate and collector currents is constant for any collector voltage and is given by the Fowler-Nordheim current I/sub FN/. Based on these observations, a simple model has been developed to calculate the I-V characteristics of a triode. By measuring the Fowler-Nordheim emission, emission area and field enhancement can be obtained assuming a value for the barrier height. Incorporating the gate current, the collector current can be calculated from I/sub c/=I/sub FN/-I/sub g/ as a function of collector voltage. The model's accuracy is best at low current density. At higher emission currents, deviations occur at low collector voltages because the constancy of gate and collector currents is violated. >

Resonant tunneling diodes and transistors with a one-, two-, or three-dimensional electron emitter

We calculate the current versus emitter to collector voltage, current versus emitter Fermi energy, and current versus potential energy in the quantum well for double-barrier resonant tunneling devices having a one-, two-, or three-dimensional electron emitter. We consider both transistor and diode operation of the devices. For each device, the current is obtained using a method which describes the effects of finite temperature, finite voltage, and free-electron motion perpendicular to the tunneling direction as independent convolutions.

Polyimide-related design considerations in a bipolar technology

It is found that a spurious leakage path from the emitter to the collector of a lateral p-n-p or a trench-defined n-p-n device may be induced by the applied collector voltage. This voltage influences the surface potential at the emitter-base junction through the charging of the polyimide used as interlevel dielectric or as trench fill, respectively. A simple model of the effect is developed, and several successful process features are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Direct Energy Recovery from Unneutralized Ion Beams in a Negative-Ion-Beam-Based Neutral Beam Injection System

This paper reports on a beam direct energy convertor (BDC) designed to recover unneutralized ion beam energies in a 500-keV negative-ion-based deuterium neutral injection system for the Fusion Experimental Reactor of Japan Atomic Energy Research Institute. A newly developed three-dimensional beam transport code KUNABE-3 is used. Due to approximately equal fractions of unneutralized D{sup +} and D{sup {minus}} beams flowing from the gas neutralizer, electrostatic electron suppression is efficient. Also, magnetic separation and deflection of both species by a 1-kG magnetic field are efficiently applicable. Under suitable energy recovery conditions, perfect collection of both positive and negative ion beams is theoretically achievable, even for a collector voltage of {plus minus}480 kV, resulting in 96% energy recovery efficiency. Within {plus minus}10% deviation from the reference parameters, the designed BDC shows excellent performance for such parameters as magnetic fields, incident beam energies, and gas line densities.

AlGaAs/Ge/GaAs heterojunction bipolar transistors grown by molecular beam epitaxy

An N-Al/sub 0.22/Ga/sub 0.78/As emitter, p-Ge base, and n-GaAs collector (AlGaAs/Ge/GaAs) heterojunction bipolar transistor (HBT) in the emitter-up configuration grown by molecular beam epitaxy is discussed. Devices exhibited common-emitter current gains of as high as 300 at a collector current density of 2000 A/cm/sup 2/ and a collector voltage of 4 V. As the device area is reduced from 50*50 to 10*40 mu m, the current gain did not show significant changes, suggesting a low surface recombination velocity in the Ge base.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Miniband Base Transistor

A new type of transistor called the miniband base transistor is proposed and fabricated. The miniband base transistor uses, as an entire base layer, a superlattice of the same conduction type as an emitter and a collector. The superlattice base is designed so that the injected electrons are in the first excited miniband, while base current carriers are in the ground miniband. The minigap between these two minibands is expected to suppress LO-phonon scatterings and to increase the current gain. The transistor is fabricated using an AlGaAs/GaAs superlattice. Electrical measurements indicate that the superlattice base is effective for improving the current gain of the hot-electron transistor at small collector voltage.

Substrate current reduction techniques for BiCMOS DRAM

Substrate current (I/sub BB/) reduction techniques useful to BiCMOS DRAM's are proposed through a comparison of the I/sub BB/ characteristics for a BiCMOS driver and a CMOS driver and through a clarification of the I/sub BB/ generation mechanism. Four key results are obtained. One is that the I/sub BB/ of conventional BiCMOS drivers is unacceptably high, i.e, three times larger than that of CMOS drivers. Another is that the excessive I/sub BB/ of BiCMOS drivers is generated by the saturation of bipolar transistors, which results from a collector voltage decrease caused by large amounts of collector current flowing through the collector saturation resistance r/sub cs/. The third result concerns proposals for I/sub BB/ reduction techniques. One features two collector outputs terminals for avoiding the r/sub cs/ effect and the other features application of a low supply voltage for the base. The last result is that BiCMOS drivers using the I/sub BB/ reduction techniques make it possible to achieve 1-Mbit BiCMOS DRAM'S with I/sub BB/ levels comparable to those of conventional CMOS DRAM's. >

Theory of the quantum well emission transistor

We present a theoretical analysis of the physical processes and high-speed performance of the recently proposed quantum well emission transistor employing quantum properties of electrons in a single quantum well (QW). The physical mechanism of device operation is based on an exponentially strong variation of the thermionic emission from the QW to the collector induced by the charge density modulation in the QW by the gate voltage. The calculation is performed for the selected structure optimized for the highest device performance.The most essential part of calculation is related to the effect of collector and gate voltages on the ground-state energy in the QW. A variational approach is used to take into account the presence of electrons in the QW. The analysis presented shows a high potential of this device for high-speed, large current drive applications.