带有复合掺杂层集电区的InP/InGaAs/InP DHBT直流特性分析

设计了一种新结构InP/InGaAs/InP双异质结双极晶体管(DHBT),在集电区与基区之间插入n -InP层,以降低集电结的导带势垒尖峰,克服电流阻挡效应.采用基于热场发射和连续性方程的发射透射模型,计算了n -InP插入层掺杂浓度和厚度对InP/InGaAs/InP DHBT集电结导带有效势垒高度和I-V特性的影响.结果表明,当n -InP插入层掺杂浓度为3×1019cm-3、厚度为3nm时,可以获得较好的器件特性.采用气态源分子束外延(GSMBE)技术成功地生长出InP/InGaAs/InP DHBT结构材料.器件研制结果表明,所设计的DHBT材料结构能有效降低集电结的导带势垒尖峰,显著改善器件的输出特性.     

Comparison of heterostructure-emitter bipolar transistors (HEBTs) with InGaAs/GaAs superlattice and quantum-well base structures

The characteristics of InGaP/GaAs heterostructure-emitter bipolar transistors (HEBTs) including conventional GaAs bulk base, InGaAs/GaAs superlattice-base, and InGaAs quantum-well base structures are presented and compared by two-dimensional simulation analysis. Among of the devices, the superlattice-base device exhibits a highest collector current, a highest current gain and a lowest base–emitter turn-on voltage attributed to the increased charge storage of minority carriers in the InGaAs/GaAs superlattice-base region by tunneling behavior. The relatively low turn-on voltage can reduce the operating voltage and collector–emitter offset voltage for low power consumption in circuit applications. However, as to the quantum-well base device, the electrons injecting into the InGaAs well are blocked by the p⁺-GaAs bulk base and it causes a great quantity of electron storage within the small energy-gap n-type GaAs emitter layer, which significantly increases the base recombination current as well as degrades the collector current and current gain.     

Temperature dependence of avalanche multiplication in InP-based HBTs with InGaAs/InP composite collector: device characterization and physics model

Recent efforts are being focused on improving the breakdown of InP-based heterojunction bipolar transistors (HBTs) towards high-power applications. A fundamental understanding of the temperature dependence of breakdown and its physics mechanism in these devices is important. In this work, a detailed characterization of temperature-dependent collector breakdown behavior in InP DHBTs (DHBTs) with an InGaAs/InP composite collector is carried out. A physics model for the prediction of temperature-dependent breakdown in lnP/InGaAs composite collector is developed. We found that, although the variation of impact ionization coefficient due to the change of temperature may affect the device breakdown, the temperature-dependence of breakdown in the lnGaAs/InP composite collector could be significantly affected by the carrier transport in the InGaAs region. As temperature is increased, the increase in the contribution of InGaAs layer to the junction breakdown due to the reduction of electron energy relaxation length could be the root cause of the reduction of junction breakdown voltage. Good agreement between the physics model and experimental data demonstrate the validities of the proposed physics model to predict the temperature dependent breakdown characteristics for InP DHBTs.     

Light-emitting transistor based on real-space transfer: electricaland optical properties

The charge injection transistor is implemented in InGaAs/InAlAs/InGaAs heterostructure material, grown by molecular beam epitaxy. A complementary collector of p-type conductivity is used for the first time. The real-space transfer of hot electrons leads to a luminescence signal proportional to the injection current. The radiative efficiency is significantly enhanced by a double-heterostructure design of the collector active region, which confines the injected minority carriers. The internal quantum efficiency of the light-emitting transistor is comparable to that of light-emitting diodes. Due to peculiar symmetry of real-space transfer, the optical output signal follows an exclusive-OR function of input voltages. Functional logic operation of the device is demonstrated at room temperature     

Degradation of DC characteristics of InGaAs/InP singleheterojunction bipolar transistors under electron irradiation

The effects of high-energy (~1 MeV) electron irradiation on the dc characteristics of InGaAs/InP single heterojunction bipolar transistors (SHBT's) are investigated. The device characteristics do not show any significant change for electron doses <10¹⁵/cm². For higher doses, devices show a decrease in collector current, a degradation of common-emitter current gain, an increase in collector saturation voltage and an increase in the collector output conductance. A simple SPICE-like device model is developed to describe the dc characteristics of SHBT's. The model parameters extracted from the measured dc characteristics of the devices before and after irradiation are used to get an insight into the physical mechanisms responsible for the degradation of the devices     

Pseudomorphic AlInP/InP heterojunction bipolar transistors

Novel InP-based heterojunction bipolar transistors (HBTs) using an AlInP pseudomorphic emitter, together with an InP base and collector, have been fabricated. By using InP as both base and collector, the advantage of high electron velocity and high breakdown field of InP collectors are obtained without the problem associated with the energy barrier between the more standard InGaAs/InP base and collector heterojunction. Epitaxial layers were grown by gas-source molecular beam epitaxy (GSMBE). The 200 Å pseudomorphic emitter had an aluminium fraction of 15%, sufficiently suppressing hole injection from the base. The DC gain for 40×40 μm² devices reached 18. The breakdown voltage BV_CEO of 10 V is an improvement over devices with InGaAs base and collector layers     

A novel InP/InGaAs TEBT for ultralow current operations

A novel InP/InGaAs tunneling emitter bipolar transistor (TEBT) is fabricated and demonstrated. The studied device exhibits a very small collector-emitter offset voltage of 40 mV and an extremely wide operation regime. The operation region is larger than 11 decades in magnitude of collector current (10/sup -12/ to 10/sup -1/A). A current gain of 3 is obtained even if the device is operated at an ultralow collector current of 3.9 /spl times/ 10/sup -12/A (1.56 /spl times/ 10/sup -7/A/cm/sup 2/). Furthermore, the common-emitter breakdown voltage of the studied device is higher than 2 V. Consequently, the studied device shows a promise for low supply voltage, and low-power consumption circuit applications.     

Investigation of the degradation mechanisms of InP/InGaAs DHBT under bias stress conditions to achieve electrical aging model for circuit design

The reliability of InP/InGaAs DHBT under high collector current densities and low junction temperatures is analyzed and modeled. From the Gummel characteristics, we observe several types of device degradation, resulting from the long term changes of base and collector current in both lower and higher base–emitter voltage ranges which impacts the reduction of DC current gain. In this paper, we investigate the underlying physical mechanism of base and collector current degradation with the help of TCAD device simulation. We chose the HICUM model level2 for the modeling purpose to evaluate the drift of model parameters according to stress time. The evolution of the model parameters is described with suitable equations to achieve a physics based compact electrical aging model. The aging laws and the parameter evolution equations with stress time are implemented in compact electrical aging model which allows us to simulate the impact of device failure mechanisms on the circuit in operating conditions.     

Temperature dependent DC characteristics of an InP/InGaAs/InGaAsPHBT

We report the DC characteristics of n-p-n InP/InGaAs/InGaAsP HBT's which have a composite-collector structure designed to improve the breakdown and gain. The devices exhibit common-emitter current gain of greater than 8 for over 9 orders of magnitude of collector current and breakdown voltages greater than 10 V. The DC gain for a typical device decreases from 40 at room temperature to 8 at 90 K. Over the same temperature range the collector-current ideality factor increases from 1.04 to 1.46, and the base current ideality factor is 0.05 to 0.1 larger than these values. We suggest that the high collector-current ideality factor and the lower gain at the lower temperatures is due to the increasing importance of tunneling of current across the emitter-base junction. The devices with the InGaAs/InGaAsP composite-collector structure offer better common-base turn-on behavior than those with InGaAs/InP as the collector structure, without the breakdown behavior being compromised     

Collector offset voltage of heterojunction bipolar transistorsgrown by molecular beam epitaxy

The collector-emitter offset voltages of InAlAs/InGaAs heterojunction bipolar transistors grown by molecular-beam epitaxy are discussed. Both the difference between emitter and collector areas and electrical asymmetry between emitter and collector junctions in these mesa-isolated transistors account for the offset voltages observed. Devices exhibited offset voltages in the range of 50-300 mV, depending on the structures and device sizes. Several electrical and geometrical factors affecting the offset voltage are discussed in detail     

A p-channel BICFET in the InGaAs/InAlAs material system

The bipolar inversion-channel field-effect transistor (BICFET) relies on a field-effect mechanism to induce and modulate an inversion layer placed at the heterojunction interface. The device was fabricated using molecular beam epitaxy. A current gain of ~15 has been achieved at a current density J of ~8×10³ A/cm² at 300 K. At 77 K, the gain rises to 40 with J=2×10⁴ A/cm². This gain, which follows theoretical predictions, continuously increases with collector current and is limited only by the amount of heat generated in a large-area device. Because of its potential for ballistic transport in the collector, the InGaAs/InAlAs BICFET should be very attractive for high-speed applications     

Avalanche multiplication in InP/InGaAs double heterojunctionbipolar transistors with composite collectors

The experimental and theoretical studies of electron multiplication in InP/InGaAs double heterojunction bipolar transistors (DHBT's) with an InGaAs/InP composite collector are carried out. Both local electric field model and energy model are used to investigate the electron impact ionization in the composite collector. The analysis reveals that the nonlocal effect of the electron impact ionization in the composite collector is responsible for the suppression of the contribution of electron multiplication in the InGaAs layer. Experimental results for the fabricated devices were compared with the theoretical calculations, indicating that the conventional impact ionization models based on the local electric field significantly overestimate the electron multiplication for the composite collector. The energy model which takes into account the nonlocal effect is found to provide a more accurate prediction of electron multiplication for the DHBT's     

InP/InGaAs double-heterojunction bipolar transistors for high-speedoptical receivers

We fabricated monolithically integrated pin/HBT photoreceivers using FPIGA (full-potential InGaAs) DHBT's with various collector thicknesses. An HBT figure-of-merit was deduced from the relationship between measured bandwidths of the preamplifiers and the f_T's and f_max's of the DHBT's. A phenomenological device model of the DHBT's is proposed to find the optimum collector thickness that gives the highest bandwidth of the photoreceivers. Finally, we discuss the feasibility of monolithically integrating a pin-PD, preamplifier, buffer amplifier, and D-type flip-flop with an operating speed of 40 Gbit/s     

Simulated analysis for InGaP/GaAs heterostructure-emitter bipolar transistor with InGaAs/GaAs superlattice-base structure

A novel InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) with InGaAs/GaAs superlattice-base structure is proposed and demonstrated by two-dimensional analysis. As compared with the traditional HEBT, the studied superlattice-base device exhibits a higher collector current, a higher current gain of 246, and a lower base–emitter (B–E) turn-on voltage of 0.966 V at a current level of 1 μA, attributed to the increased charge storage of minority carriers in the InGaAs/GaAs superlattice-base region by tunneling behavior. The low turn-on voltage can reduce the operating voltage and collector–emitter offset voltage for low power consumption in circuit applications.     

A new functional optical-electrical switch using a multi-emitterheterojunction phototransistor

We propose a new functional optical-electrical switching device: a multi-emitter heterojunction photo-transistor (ME-HPT) using a multi-emitter heterojunction bipolar transistor (ME-HBT) structure. In this device, the collector current (I_C) can be controlled by not only the incident radiant power (P₀) but also the voltage difference between emitters (V_EE). We fabricated ME-HPT's using InGaAs/InP heterostructures and confirmed the normal operation. Using only one ME-HPT, we have successfully demonstrated a new functional optical-electrical switching operation, which can switch on only when both the electrical and optical signals are high     

Novel fabrication of C-doped base InGaAs/InP DHBT structures for high speed circuit applications

We have fabricated InGaAs/InP based DHBTs for high speed circuit applications. A process involving both wet chemical and ECR plasma etching was developed. Carbon was employed as the p-type dopant of the base layer for excellent device stability. Both the emitter–base and base–collector regions were graded using quaternary InGaAsP alloys. The extrinsic emitter–base junction is buried for junction passivation to improve device reliability. The use of an InP collector structure with the graded region results in high breakdown voltages of 8-10 V, with no current blocking. The entire structure is encapsulated with spin-on-glass. These devices show no degradation in d.c. characteristics after operation at an emitter current density of 90 kA cm⁻² and a collector bias, V_CE, of 2 V at room temperature for over 500 h. Typical common emitter current gain was 50. An f_t of 80 and f_max of 155 GHz were achieved for 2×4 μm² emitter size devices.     

DC, RF, and noise characteristics of carbon-doped base InP/InGaAsheterojunction bipolar transistors

The first successful demonstration of high-performance InP/InGaAs heterojunction bipolar transistors utilizing a highly carbon-doped base is reported. The detailed device characteristics including dc, RF, and noise performance have been investigated. For the first time base layers free of hydrogen passivation have been obtained using chemical beam epitaxy. The HBT's showed almost ideal dc characteristics; a gain independent of collector current, a near unity ideality factor, a very small offset-voltage, and a high breakdown voltage. Devices having two 1.5 μm×15 μm emitter fingers exhibited a maximum f_T of 115 GHz and f_max of 52 GHz. The device also exhibited a minimum noise figure of 3.6 dB and associated gain of 13.2 dB at a collector current level of 2 mA where a f_T of 29 GHz and f_max of 23 GHz were measured. The nearly ideal dc characteristics, excellent speed performance, and RF noise performance demonstrate the great potential of the carbon-doped base InP/InGaAs HBT's     

带有阶梯缓变集电区的InP/InGaAs/InP DHBT材料研究

设计并生长了一种新的InP/InGaAs/InP DHBT结构材料,采用在基区和集电区之间插入两层不同禁带宽度的InGaAsP四元系材料的阶梯缓变集电结结构,以解决InP/InGaAs/InP DHBT集电结导带尖峰的电子阻挡效应问题。采用气态源分子束外延(GSMBE)技术,通过优化生长条件,获得了高质量的InP、InGaAs以及与InP晶格相匹配的不同禁带宽度的InGaAsP外延材料。在此基础上,成功地生长出带有阶梯缓变集电区结构的InP基DHBT结构材料。     

DC and microwave noise transient behavior of InP/InGaAs doubleheterojunction bipolar transistor (DHBT) with polyimide passivation

DC and microwave noise transient behavior of InP/InGaAs double heterojunction bipolar transistor (DHBT) with polyimide passivation is reported in this paper for the first time. The base transient current is believed to be due to the change of surface potential near the base-emitter junction perimeter at the polyimide/emitter interface resulting from a decrease in the amount of trapped electrons in the polyimide. We also find that the surface potential on the sidewall of collector-emitter affected by the charge trapping and detrapping in polyimide may induce a parasitic polyimide field effect transistor along the surface of the base-collector junction which results in an excess collector transient current. These base and collector current transients result in associated transient of broadband shot noise. The time dependence of microwave noise figures due to the excess transients is also investigated. The better understanding of the mechanisms of the noise transient behavior of the InP HBT device is very useful to improve the device and circuit reliability     

准平面型InAlAs/InGaAs异质结双极晶体管和单片集成激光器驱动电路

提出和制作了准平面型InAlAs/InGaAs异质结双极晶体管。该管主要采用硅离子注入法在半绝缘磷化铟衬底中形成隐埋型集电区以代替台面型集电区。晶体管的实测结果如下:h_(fe)=100,f_T=10GHz(V_(CE)=3V,I_c=10mA)。作为单片光电集成方面的实例,研制成功了由三个InGaAs/InAlAsHBT和一个电阻组成的激光器驱动电路,其电流调制速率高达4Gbit/s。