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A compound emitter heterojunction bipolar transistor (HBT) structure that incorporates an additional heterojunction within the emitter for minority carrier confinement has been proposed. In this new device configuration, the single wide band‐gap emitter layer in a conventional HBT is replaced by two sub‐layers of wide band‐gap material, with the sub‐layer nearer the base having a narrower band‐gap. By means of numerical simulations, the compound emitter HBT was found to perform better than comparable conventional HBTs. With the AlGaAs(n) / GaAs heterostructure system, the optimum compound emitter HBT structure was found to be Al0.3Ga0.7As(n) ‐ Al0. 2Ga0.8As(n) / GaAs with grading at the two hetero‐interfaces. It has a low turn‐on voltage that is almost identical to that of a homojunction GaAs bipolar transistor with similar doping conditions. Compared with a conventional single emitter layer Al0.3Ga0.7As/GaAs HBT, the optimum compound emitter HBT has an enhancement in the current gain by approximately 2 folds, an improvement in the uniform current gain region from 2 to 4 decades of collector current density, and a slight increase in the unity‐gain cut‐off frequency fT by about 7 %.

We present an abstract mathematical and numerical analysis for Drift‐Diffusion equation of heterojunction semiconductor devices with Fermi‐Dirac statistic. For the approximation, a mixed finite element method is considered. This can be profitably used in the investigation of the current through the device structure. A peculiar feature of this mixed formulation is that the electric displacement D and the current densities jn and jp for electrons and holes, are taken as unknowns, together with the potential φ and quas‐Fermi levels φn and φp. This enably D, jn and jp to be determined directly and accurately. For decoupled system, existence, uniqueness, regularity and stability results of the approximate solution are given. A priori and a posteriori error estimates are also presented. A nonlinear implicit scheme with local time steps is used. This algorithm appears to be efficient and gives satisfactory results. Numerical results for an heterojunction bipolar transistor, In two dimension, are presented.

We present a semi‐quantum model including tunneling effects across an abrupt heterojunction. The discontinuity of the effective masses and the energy bands are considered. The quantum transmission conditions for the quasi‐Fermi levels are obtained using WKB approximation. We use mixed finite element approach and a two dimensional mesh which is double‐valued for quasi‐Fermi levels at a heterojunction. A GaAs/GaAIAs heterojunction diode is then simulated using both drift‐diffusion and semi‐quantum model by varying doping density at low temperature.

The purpose of this paper is to investigate the dependence of dark current on threading dislocations (TDs) in relaxed Ge layer for Ge/Si heterojunction photodetectors.

The analysis of the effects of TDs is based on SRH generation and recombination mechanism used in two‐dimensional drift‐diffusion numerical simulation.

It is found that the TDs in Ge layer acting as the recombination centers lead to large dark current densities of devices, and the recombination rate is affected by the impurity out‐diffusion from Si substrate. Besides, the TDs, being the acceptor‐like defects simultaneously, form band barrier at Si/Ge interface with lightly doped Si substrates, thus limiting the minority carrier transport and resulting in low dark current densities.

The simulation results are excellently consistent with the experimental data and indicate that the reduction of threading dislocation densities (TDDs), especially in Ge buffer layer, dramatically decreases dark currents densities of Ge/Si photodetectors. The investigation can be applied to imbue devices with desired characteristics.

The purpose of this paper is to examine the growth and characterization of the two different compound semiconductors, namely, n-zinc oxide (ZnO) and p-gallium antimonide (GaSb). In this paper, fabrication and characterization of n-ZnO/p-GaSb heterojunction diode is analyzed.

Thermo vertical direction solidification (TVDS) method was used to synthesize undoped GaSb ingot from high purity Ga (5N) and Sb (4N) host materials. Thermal evaporation technique is used to prepare a film of GaSb on glass substrate from the pre-synthesized bulk material by TVDS method. Undoped ZnO film was grown on GaSb film by sol–gel method by using chemical wet and dry (CWD) technique to fabricate n-ZnO/p-GaSb heterojunction diode.

The formation of crystalline structure and surface morphological analysis of both the GaSb bulk and film have been carried out by x-ray diffraction (XRD) analysis and scanning electron microscopy analysis. From the XRD studies, the structural characterization and phase identification of ZnO/GaSb interface. The current–voltage characteristic of the n-ZnO/p-GaSb heterostructure is found to be rectifying in nature.

GaSb film growth on any substrate by thermal evaporation method taking a small piece of the sample from the pre-synthesized GaSb bulk ingot has not been reported yet. Semiconductor device with heterojunction diode by using two different semiconductors such as ZnO/GaSb was used by this group for the first time.

This model is intended to simulate the large signal performance of heterojunction bipolar transistors for use in high power, high frequency, oscillators, amplifiers, and mixers. A temperature model which includes velocity overshoot and carrier energy effects has been developed. The model is used to calculate the large signal “Y” parameters of an HBT. A comparison is made between predicted power performance using the “Y” parameters and a fully numerical, time domain computation. Advantages and disadvantages of each approach are given.

Some results related to the algorithmic behaviour in semiconductor devices numerical simulations (‐static case‐), using mixed finite elements and operator splitting techniques have been presented in. The drift‐diffusion model written with the electrostatic potential φ and the quasi‐Fermi levels φn and φp is used.

This paper is devoted to the numerical study, using the deterministic particle method, of the parallel transport of a bidimensional electron gas confined in a potential well near a heterojunction interface. The geometry makes it possible to solve independently the transport under the electric field and the well shape. We simulate the electronic transport with a kinetic model and use the deterministic particle method. As for the description of the potential well, we use different models and compare their influence on the thermodynamic equilibrium and on the transport properties of the electron gas.

Numerical device simulation is developed to study the steady‐state and transient current‐voltage characteristics of double heterostructure AlGaAs/GaAs PNPN electro‐photonic device when its performance is influenced by the presence of interface and bulk recombination mechanism. The simulation results show that the holding current and voltage and the breakover point are strongly affected by varying the minority carrier lifetime at outer heterojunctions. Numerical results also indicate that shortening the minority carrier lifetime in the inner PN homojunction region only increases the OFF‐state current. These results are in agreement with experimental data on AlGaAs/GaAs PNPN devices. The numerical modelling approach taken in this study is shown to be essential in the design and optimization of PNPN switch.

An efficient numerical model of heterojunction bipolar transistor high frequency performance is proposed. The developed model is based on the ensemble Monte Carlo particle simulator. The validity and accuracy of the model are verified by comparing of the results of the model prediction with the experimental dates. The role of the thickness of the collector junction on the transistor cut‐off frequency is investigated and it is found that transistor cut‐off frequency as a function of the collector thickness has a maximum.