Single Heterojunction Bipolar Transistors Research Articles

Modeling and analysis for the effects of gamma irradiation on the DC and AC performance in InGaP/GaAs SHBTs

ABSTRACTThe effects of gamma irradiation on the DC and AC characteristics of InGaP/GaAs single heterojunction bipolar transistors (SHBTs) are investigated comprehensively for the first time, which is based on experimental data before irradiation, after irradiation and after annealing. A simplified VBIC device model is developed to describe the DC and AC characteristics of the devices. The model parameters are extracted from experimental data before irradiation, after irradiation and after annealing. Finally, the degraded rates of model parameters are used to study the radiation-induced degradation of the device performance.

How does technological parameters impact the static current gain of InP-based Single Heterojunction Bipolar Transistor?

<p>In telecommunication systems, Heterojunction Bipolar Transistors (HBTs) are used extensively due to their good electrical characteristics. The work presented in this paper aims to enhance the electrical performance of the InP / InGaAs Single Heterojunction Bipolar Transistor (SHBT) in terms of the static current gain β. Silvaco’s TCAD tools were used for the simulation of the output characteristics of the studied electronic device. Initially, we used the interactive tool Deckbuild to define the simulation program and the device editor DevEdit to design the device structure, and we also used the simulator Atlas which allows the prediction of the electrical characteristics of most semiconductor devices. Because of several phenomena occuring within the electronic device SHBT, we added some physical models included in the simulator such as SRH, BBT.STD. Afterwards, we investigated the influence of doping concentrations of the base and the collector N<sub>b</sub> and N<sub>c</sub> on the electrical performance of the InP/InGaAs SHBT, and particularly in terms of the static current gain β. Finally, based on optimal values of the selected parameters, we have defined an optimized device that has a highest current gain β.</p>

Investigation of the static current gain for InP/InGaAs single heterojunction bipolar transistor

<p>Heterojunction Bipolar Transistors are being used increasingly in communication systems due to their electrical performances. They are considered as excellent electronic devices. This paper presents an investigation of the static current gain β based on two technological parameters related to the device geometry for InP/InGaAs Single Heterojunction Bipolar Transistor (SHBT). These parameters are the base width and the emitter length . We used Silvaco’s TCAD tools to design the device structure, and to extract the static current gain β from I-V output characteristics figures. According to this investigation, we determined the optimal values of the examined parameters which allow obtaining the highest static current gain β.</p>

Influence of Al/Si Codiffusion on Current Gain Deterioration in AlGaN/GaN Single Heterojunction Bipolar Transistors

AlGaN/GaN single heterojunction bipolar transistors (SHBTs) without using regrown emitter junction are demonstrated. Secondary ion mass spectroscopy analysis shows that a severe codiffusion of Al and Si exists in AlGaN/GaN heterostructures grown at 780 °C. The altered composition and doping profiles greatly degrade the common-emitter current gain of AlGaN/GaN HBTs to ≤0.8. A GaN spacer layer is inserted at the emitter-base junction to alleviate this problem. In an AlGaN/GaN HBT structure inserted with a 20 nm unintentionally doped GaN spacer layer, a current gain $\beta $ about 2 is achieved.

Large Signal Model of Heterojunction Bipolar Transistor InP/InGaAs as an Optoelectronic Mixer

A large-signal model of InP/InGaAs single Heterojunction Bipolar Transistor (HBT) has been developed considering spectral performance and mixing. This model is based on Gummel Poon BJT model. HBT InP/InGaAs has been modeled and analyzed in this paper as an optoelectronic mixer (OEM). The HBT proposed was simulated by considering the wavelength of 1310 nm for an up-conversion frequency of 30 GHz. Its characteristics was further investigated to develop the appropriate structure device for OEM application. This proposed HBT InP/InGaAs can be potentially implemented in the broadband Radio over Fiber (RoF) system to perform photodetection and frequency up-conversion.

Proton irradiation effects on InGaP/GaAs single heterojunction bipolar transistors

The irradiation effects of low energy proton on both Direct Current (DC) and the Radio Frequency (RF) performance of InGaP/GaAs single heterojunction bipolar transistors (SHBTs) are investigated with fluence up to 5×1012protons/cm2. The current gain in RF and the cutoff frequency (fT) show a little degradation even at proton fluence of 5×1012/cm2. The open-collector technique is used to extract the access resistances. Meanwhile 10MeV proton irradiation is also investigated in order to compare the differences induced by different proton energies. The results indicate that InGaP/GaAs HBT is tolerant to proton irradiation.

Current Gain and Offset Voltage in an InGaP/GaAsSb/GaAs Double Heterojunction Bipolar Transistor

An In0.5Ga0.5P/GaAs0.93Sb0.07/GaAs heterostructure is grown by metal-organic chemical vapor deposition and demonstrated to be an alternative to InGaP/GaAs systems for use in single heterojunction bipolar transistors (SHBTs). The In0.5Ga0.5P/GaAs0.93Sb0.07/GaAs double heterojunction bipolar transistor (DHBT) device structures are identical to the control SHBTs except for the incorporation of antimony to the base layer. The InGaP/GaAsSb/GaAs DHBT has a lower turn-on voltage than the control InGaP/GaAs SHBT. Details of the effect of the base current on the offset voltage in the studied devices are explored. The dc current gain β of the InGaP/GaAsSb/GaAs DHBT is virtually independent of collector current at 300 K. The current gain of the GaAsSb-based DHBT is greater than 40 at a very small collector current of 1 μA at 300 K. The dependence of the current gain on temperature at various collector currents is discussed. The variation of β with temperature is slight at high currents over the range of 300 K-390 K. Furthermore, the current gain of the InGaP/GaAsSb/GaAs DHBT exhibits almost no dependence on the collector-base voltage VCB, demonstrating the nonblocking “type-II” band lineup at the base/collector heterojunction.

The model parameter extraction and simulation for the effects of gamma irradiation on the DC characteristics of InGaP/GaAs single heterojunction bipolar transistors

In this article, we report the effect of gamma irradiation on the DC characteristics of InGaP/GaAs single heterojunction bipolar transistors (SHBTs) based on the simulation with the extracted model parameters from experiment data before irradiation, after irradiation and after annealing. A simplified Vertical Bipolar Inter-Company (VBIC) static model is proposed to study the operational mechanism and the DC characteristics of SHBTs. The results show that the defects induced by irradiation are responsible for the changes on the DC characteristics of the devices.

$\hbox{InGaP/GaAs}_{0.57}\hbox{P}_{0.28} \hbox{Sb}_{0.15}/\hbox{GaAs}$ Double HBT With Weakly Type-II Base/Collector Junction

We report on the dc characteristics of an InGaP/ GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.57</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.28</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.15</sub> /GaAs double heterojunction bipolar transistor (DHBT). In comparison with control InGaP/GaAs single heterojunction bipolar transistors (SHBTs), the DHBT shows a lower turn-on voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BE, on</sub> ) by ~ 70 mV, a lower knee voltage up to J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ~ 40 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and less temperature-sensitive current gain. The validity of reciprocity in the Gummel plot suggests no potential spikes at the emitter/base and base/collector (BC) junctions of the DHBT. By considering the differences, in terms of the built-in voltage of the BC junction, the Fermi level in the base, and the renormalized energy gap of the base, between the GaAsPSb DHBT and the control InGaP/GaAs SHBT, we conclude that the heavily p-doped GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.57</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.28</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.15</sub> base and the lightly n-doped GaAs collector are in weakly type-II band alignment with a conduction and valence band offset of 44 and 221 meV, respectively. These findings indicate that GaAsPSb is a promising base material for DHBTs operating at high temperature and low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BE, on</sub> conditions without suffering from the collector current blocking.

Ultra high-speed InP/InGaAs SHBTs with/t and/max of 185 GHz

An InP/InGaAs single heterojunction bipolar transistor (SHBT) with high maximum oscillation frequency (fmax) and high cutoff frequency (ft) is reported. Efforts have been made to maximize fmax and ft simultaneously including optimizing the epitaxial structure, base-collector mesa over-etching and base surface preparation. The measured ft and fmax both reached 185 GHz with an emitter size of 1 × 20 μm2, which is the highest fmax for SHBTs in mainland China. The device is suitable for ultra-high speed digital circuits and low power analog applications.

Estimation of Collector Current Spreading in InGaAs SHBT Having 75-nm-Thick Collector

We investigated collector current spreading in InGaAs single heterojunction bipolar transistors (SHBTs) having a collector thickness of 75nm. SHBTs were fabricated with three different emitter widths — 200, 400, and 600nm — and the highest cutoff frequency that was obtained was 468GHz. The relationship between the current density at the highest cutoff frequency and the emitter width could not be used to estimate the current spreading because it was independent of the collector-base voltage. However, the relationship between the current density with the increase in the total collector-base capacitance and the emitter width indicates current spreading in the collector. The current spreading was estimated to be approximately 90nm.

Magnetotransport characterization of surface-treated InP/InGaAs heterojunction bipolar transistors

The results of surface modification induced effects on InP/InGaAs single heterojunction bipolar transistors, as revealed by magnetotransport experiments, are described here. The surface treatments included both sulphur-based surface passivation and ion bombardment-induced surface damage. The former is known to improve device characteristics and the latter to degrade device operation. In this work the aim was to assess these techniques for tailoring device performance for surface sensing applications. Device characteristics were found to be sensitive to surface preparation prior to measurements. Measurements revealed that surface treatments that improve device performance also reduce sensitivity to external magnetic fields while treatments that degrade performance make devices more sensitive to externally applied magnetic fields.

On the breakdown behaviors of InP/InGaAs based heterojunction bipolar transistors (HBTs)

The breakdown behaviors of InP/InGaAs single heterojunction bipolar transistor (SHBT) and double heterojunction bipolar transistor (DHBT) are studied and demonstrated. By using a composite collector structure at the base–collector heterojunction, the undesired current-blocking effect, switching, hysteresis phenomenon usually found in an InP/InGaAs conventional DHBT are not observed in our DHBT device. Experimentally, as compared with the studied SHBT, the studied DHBT reveals the enhanced breakdown voltages, lower collector leakage current I CO, and smaller electron impact ionization α. Moreover, the temperature-dependent electron impact ionization characteristics and electrical reliability for both devices are also studied. Therefore, the studied DHBT device provides the promise for millimeter-wave and power circuit applications.

High performance pnp AlGaN∕GaN heterojunction bipolar transistors on GaN substrates

We fabricated pnp AlGaN∕GaN heterojunction bipolar transistors (HBTs) with various emitter areas on GaN substrates and investigated their common-emitter current-voltage and high-power characteristics at room temperature. The HBTs with an emitter area of 30×50μm2 exhibited a high performance: a maximum current gain of 85 at a collector current of 30mA and a maximum collector current density of 7.3kA∕cm2 at a collector-emitter voltage of 30V, which corresponds to the maximum power dissipation density of 219kW∕cm2. The current gain and the collector current density increased compared to those on sapphire substrates. For the HBT with the emitter area of 270×450μm2, the current gain was still as high as 47 and the maximum collector current reached as high as 1A, and this single HBT showed a high-power dissipation of 30W. This high performance of the HBTs is ascribed to the low dislocation density and relatively high thermal conductivity of the GaN substrate. Although the emitter crowding and self-heating effects remain, the obtained values are highest among pnp nitride-based HBTs.

Development of the theory for thermal damage of semiconductor structures by high-power electromagnetic radiation

Three mathematical models for the thermal damage of semiconductor structures with a single junction (diodes, FETs, single-heterojunction bipolar transistors, and photodiodes) are characterized. Similarly to the Wunsch-Bell model, the proposed models are based on solutions to the 1D heat equation. In contrast to the Wunsch-Bell model, in which the thickness of the junction is assumed infinite and a rectangular acting pulse has an infinitely short leading edge, the proposed models take into account the finite dimensions of the junction; the pulse shape; and the pulse-leading-edge steepness, which is important for any mechanism of the functional damage. Conditions for the applicability of each model for the estimation of the criterial levels of functional damage in semiconductor structures are determined. It is emphasized that the heat equation should be solved with allowance for matched initial and boundary conditions.

Comparative study on temperature-dependent characteristics of InP∕InGaAs single- and double-heterojunction bipolar transistors

Interesting temperature-dependent characteristics of InP∕InGaAs-based single-heterojunction bipolar transistor (SHBT) and double-heterojunction bipolar transistor (DHBT) devices are compared and studied. Experimentally, both studied devices show wider collector current (IC) operation regions, with over 11 decades in magnitude of collector current (IC=10−12to10−1A). However, the studied DHBT exhibits improved breakdown characteristics [common-emitter breakdown voltage (BVCEO)=8.05V and common-base breakdown voltage (BVCBO)=11.3V] and low output conductance at high temperature. Moreover, the undesired current-blocking effect, switching, hysteresis phenomenon usually found in an InP∕InGaAs conventional DHBT are not observed in the DHBT device. As compared with the studied SHBT, the studied DHBT shows a lower multiplication factor and weaker temperature dependence. Therefore, it is known that, based on experimental results, the studied DHBT device provides the promise for low-voltage and low-power circuit app...

English

The cutoff frequency performance of an NPN Si/SiGe/SiGe single-heterojunction bipolartransistor (SiGe SHBT) at high collector current densities has been analysed using a 2-D MEDICIdevice simulator. A conventional NPN Si/SiGe/Si double-heterojunction bipolar transistor(SiGe DHBT) having uniform 20 atomic per cent of germanium in the base region has beeninvestigated for comparison. The analysis shows the formation of a retarding potential barrierfor minority carrier electrons at the base-collector heterojunction of the DHBT structure. Whereas,the base-collector homojunction of the SiGe SHBT structure, having a uniform 15 atomic percent of germanium profile in its base and collector, inhibits the formation of such a retardingpotential barrier, the SHBT structure with a base-collector homojunction shows an improvedcutoff frequency at high collector current density in comparison with conventional SiGe DHBT,which makes it more promising for high speed, scaled down, field-specific applications.

Photoluminescence investigation of Be-doped Npn AlGaAs/GaAs heterojunction bipolar transistor structures

Highly complex Npn AlGaAs/GaAs single heterojunction bipolar transistor (HBT) layers with Be-doped base were investigated by photoluminescence (PL) spectroscopy. Room temperature PL shows only a broad peak of GaAs due to thermalization; 15 K PL shows five peaks. The peak at ∼1.481 eV is from a p-type GaAs base, that at ∼1.517 eV is from a low-doped GaAs layer and that at ∼1.55 eV is from a high-doped GaAs collector. The that at ∼1.849 eV is due to bound exciton recombination in an AlGaAs emitter, and that at ∼1.828 eV is due to the acceptor-related transition from the AlGaAs layer. The integrated intensity ratio of these two peaks can be used to investigate the Be outdiffusion behavior, thus optimizing the growth conditions of base. The DC current gain of the HBT structure with different growth conditions was found to be in good agreement with the PL results.

Design and analysis of a single HBT-based optical receiver front-end

In this paper, we present the design and analysis of a proposed single heterojunction bipolar transistor (HBT)-based photoreceiver front-end configuration. This configuration uses a single heterojunction bipolar transistor for both photodetection and amplification purpose. The analysis of the proposed optoelectronic integrated circuit (OEIC) receiver configuration has been carried out and performance characteristics have been determined for an InP/InGaAs HBT receiver for operation in 1.55 μm wavelength region. The proposed receiver has a reasonable sensitivity along with a high transimpedance gain and large bandwidth comparable to contemporary optical receivers based on separate detector and amplifier. Use of a single HBT in the front-end would greatly simplify the fabrication of optoelectronic integrated circuit (OEIC) receiver in the monolithic form.

Lateral scaling of 0.25 µm InP/InGaAs SHBTs with InAs emitter cap

InP/InGaAs single heterojunction bipolar transistors (SHBTs) have been fabricated using a highly doped InAs emitter cap for a 50% reduction in emitter resistance to allow aggressive lateral scaling to increase fMAX. Type I InP SHBTs have been fabricated with 0.25 µm emitter widths and achieve fMAX values as high as 478 GHz on a laterally scaled LE=1 µm device, and maintain breakdown voltages greater than 4 V.