Quantum-well resonant tunneling bipolar transistor operating at room temperature

The first resonant tunneling bipolar transistor (RBT) is reported. The AlGaAs/GaAs wide-gap emitter device, grown by molecular beam epitaxy (MBE), contains a GaAs quantum well and two AlAs barriers between the emitter and the collector. In the common emitter configuration, when the base current exceeds a threshold value, a large drop in the collector current (corresponding to a quenching of the current gain β) is observed at room temperature, along with a pronounced negative conductance as a function of the collector-emitter voltage. These striking characteristics are caused by the quenching of resonant tunneling through the double barrier as the conduction band edge in the emitter is raised above the bottom of the first quantized subband of the well. Single-frequency oscillations are observed at 300 K. The inherent negative transconductance of these new functional devices is extremely valuable for many logic and signal processing applications.     

High-frequency current instabilities in a silicon Auger transistor

In an Auger transistor formed from an Al-SiO₂-n-Si heterojunction with a tunneling-thin oxide layer we have investigated high-frequency instabilities of S-and N-type in the collector current which arise during tunneling injection of hot electrons from the metal into the semiconductor. An Auger transistor is a new type of device in which a metal-insulator heterojunction is used as the wideband semiconductor emitter and the base of the transistor is induced by an electric field in the form of a self-consistent quantum well for holes on the silicon surface. The electrons injected from the metal into the semiconductor with a high kinetic energy (greater than 1 eV) during impact ionization generate electron-hole pairs in the region of the base-collector junction. This disrupts the current balance of the transistor and leads to the appearance of an unstable current of S-or N-type in the collector characteristics (in a circuit with a common emitter). The nature of the instability is connected with the large current gain in an Auger transistor (α>1). Fiz. Tekh. Poluprovodn. 33, 1126–1129 (September 1999)     

Bipolar transistor with quantum well base

We report in this study the modeling of a heterostructure bipolar transistor (HBT) where the base is designed as a quantum well. The transistor structure consists of a base layer of GaAs that is heavily p-type doped. The 0.024 μm base is sandwiched between wide band gap In_xGa_1?xP which composes the n-type emitter and collector layers immediately adjacent to the base. The thickness of the base was chosen so that it is comparable to the wavelength of the electrons passing though it. There are two heavily doped cap layers of InGaAs at the emitter contact. The remainder of the emitter and collector regions are composed of GaAs. The purpose of this design is to filter the energies and velocities of electrons as they pass through the base region that forms a quantum barrier to electrons and a quantum well to holes. This should result in a significant decrease of noise in comparison to that observed in non-quantum base HBTs. As expected, the thin quantum well improves the collection of injected carriers, which in turn boosts the DC gain (β) to 750 and increases the power of the novel transistor by a factor of six, in comparison to a commercially available HBT with a similar non-quantum well structure. At high frequencies, the gain of the device is increased by about 5 dB over the non-quantum base HBT that this device is based upon. Additionally, the cutoff frequency is improved from 20 to 50 GHz. Modeling of the novel transistor was done using Silvaco ATLAS?. This study will continue with the fabrication of experimental wafers.     

A theory and some characterisitcs of power transistors at high-level conditions

The concentration of injected carriers is large compared with the impurity doping concentration in the base region of a power transistor operating at high level. Carrier concentration and characteristics of a two-dimensional transistor model are calculated for this case. Emitter and base contacts are in the form of strips. Most of the injected emitter current reaches the collector while the remainder recombines in the slightly doped base region under the emitter, resulting in a current in the highly doped base contact. In addition, a recombination current generated in the base region under the base contact is added to this base current and results in a decrease of current gain. In order to analyze the base recombination current, a special transistor with divided collector contacts was prepared. In this way, the collector current due to the region under the emitter contact can be separated from the collector current due to the region under the base contact. The presented theory could be verified. Additional corrections are necessary, however, in the direction of the current in the slightly doped base region.     

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.     

A new InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT)

Excellent characteristics of an InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT) are first demonstrated. The insertion of a thin n-GaAs emitter layer between tynneling confinement and base layers effectivelty eliminates the potential spike at base-emitter junction and reduces the collector-emitter offset voltage, while the thin InGaP tunneling confinement layer is employed to reduce the transporting time across emitter region for electrons and maintain the good confinement effect for holes. Experimentally, the studied T-HEBN exhibits a maximum current gain of 285, a relatively low offset voltage of 40 mW, and a current-gain cutoff frequency of 26.4 GHz.     

Strained GaInAs-base hot electron transistor

A hot electron transistor (HET) which has a strained GaInAs base and a graded AlGaAs collector barrier was grown on a GaAs substrate by metalorganic chemical vapour deposition. In this device, the difference in energy levels between the L-band minima of the base and the top of the collector barrier is wider than that in GaAs-base HETs, which results in a common emitter current gain β (collector current/base current) as high as 30     

InGaAs/In(AlGa)As RHET's with InAs pseudomorphic base

An InGaAs/In(AlGa)As resonant-tunneling hot-electron transistor (RHET) with an INAs pseudomorphic base to increase current gain and to reduce base resistance was designed and fabricated. The conduction band discontinuity between the InAs base and the In(AlGa)As collector barrier was estimated from the thermionic current. The band discontinuity was about 0.38 eV, which agrees well with the calculated band discontinuity taking into consideration the effect of strain. The common-emitter current gain doubled and the base resistance decreased 20% compared to InGaAs-base RHETs with the same doping concentration. A current gain cutoff frequency of 65 GHz and a maximum oscillation frequency of 50 GHz at 77 K were measured     

Induced base transistor fabricated by molecular beam epitaxy

A novel three-terminal hot-electron device, the induced base transistor (IBT), has been fabricated by molecular beam epitaxy (MBE). Two-dimensional electron gas (2-DEG) induced by the applied collector field in an undoped GaAs quantum well is used as the base of the IBT. The common-base current gain α has been achieved as high as 0.96 under a collector bias of 2.5 V and an emitter current of 3 mA.     

Multiple-state resonant-tunneling bipolar transistor operating atroom temperature and its application as a frequency multiplier

A resonant-tunneling bipolar transistor with two peaks in the direct as well as in the transfer characteristics is presented. The multiple peaks are obtained by sequentially quenching resonant tunneling through the ground states of a series of double-barrier quantum wells, placed in the emitter of a Ga_0.47In_0.53As-Al_0.48In_0.52 As bipolar transistor, thus obtaining nearly equal peak currents and peak-to-valley ratios. The transistor exhibits current gain of about 70 at room temperature and 200 at 77 K. Peak-to-valley current ratios at room temperature and at 77 K are as high as 4:1 and 20:1, respectively. Frequency multiplication by factors of three and five has been demonstrated using the multiple-peak transfer characteristics of the transistor     

选择离子注入集电极技术研究

为提高超高速双极晶体管的电流增益 ,降低大电流下基区扩展效应对器件的影响 ,将选择离子注入集电区技术 (SIC)应用于双层多晶硅发射极晶体管中。扩展电阻的测试结果显示出注入的 P离子基本上集中在集电区的位置 ,对发射区和基区未造成显著影响。电学特性测量结果表明 ,经过离子注入的多晶硅发射极晶体管的电流增益和最大电流增益对应的集电极电流明显高于未经离子注入的晶体管。因此 ,在双层多晶硅晶体管中采用 SIC技术 ,有效地降低了基区的扩展效应 ,提高了器件的电学特性。     

Bipolar transistor with graded band-gap base

We report the first compositionally graded base bipolar transistor. The device grown by MBE incorporates a wide gap Al0.35Ga0.65As emitter (n = 2 × 1016/cm3 and a 0.4 ?m thick p+ (= 2 × 1018/cm3)base graded from Al0.20Ga0.80As to GaAs. DC current gain of 35 with flat, nearly ideal, collector characteristics are observed. Incorporation of a graded gap base gives much faster base transit times due to the induced quasi-electric field for electrons, thus allowing a precious tradeoff against the base resistance.     

InGaAs resonant tunneling transistors using a coupled-quantum-wellbase with strained AlAs tunnel barriers

A bipolar-type resonant tunneling transistor is studied of which the base is identical to a coupled quantum well. On the basis of the InGaAs material system strained AlAs tunnel barriers and a graded InGaAlAs emitter are used. Molecular beam epitaxy growth conditions are studied, showing a specific influence of growth temperature and arsenic pressure. We find clear evidence for resonant tunneling: a saturation of the collector current and a maximum of the transconductance with increasing base-emitter bias in a three-terminal transistor structure. A corresponding effect in a phototransistor structure is found as a maximum of differential current gain with increasing incident light intensity. Room temperature and low temperature (80 K) high-frequency properties are determined and are used to estimate the resonant tunneling time     

Lateral complementary transistor structure for the simultaneous fabrication of functional blocks

Heretofore, the schemes for fabricating a complementary transistor structure in a monolithic functional block entailed either some additional, difficult-to-control processing steps or a sacrifice in isolation of the collector regions of one type of transistor. This paper describes an isolated p-n-p transistor structure fabricated by the same technique used for the conventional all n-p-n transistor functional block without any additional processing steps. The basic p-n-p transistor has a lateral structure. During the p-type base diffusion of the n-p-n transistor, two concentric p-type regions at close distance are selectively diffused into an isolated n- type region such as that used for the collector of an n-p-n transistor. The center p-type diffused region forms the emitter and the outer ring forms the collector. The n-type spacing between these two regions serves as the base. The current gain of this transistor is not high, typically around unity. However, by amplifying the collector current of the p-n-p transistor with an n-p-n transistor, the composite transistor acts like a high gain p-n-p transistor and the composite current gain can be made comparable to that of the n-p-n transistor in the same functional block. The lateral complementary transistor has been used extensively and successfully for the fabrication of linear functional blocks such as those used in the Advanced Minuteman Program.     

High-speed InP-InGaAs heterojunction phototransistors employing anonalloyed electrode metal as a reflector

High-speed InP-InGaAs heterojunction phototransistors (HPT's) with a base terminal (three-terminal HPT's) have been fabricated. These HPT's have nonalloyed electrodes functioning as reflectors and a configuration in which light is incident through the substrate. These features lead to an increase in quantum efficiency in spite of the thin base and collector light-absorbing layers. Optical gain dependence on collector current is weak because of the low recombination current at the emitter-base interface. Maximum optical-gain cutoff frequencies of 22 and 14 GHz are obtained for a 3×3-μm² emitter HPT illuminated by 1.3- and 1.55-μm light, respectively. This HPT has the capability of operating as a high-speed heterojunction bipolar transistor (HBT) as well. A current-gain cutoff frequency (f_T) of 128 GHz is obtained for a 3×9-μm² emitter HBT fabricated on the same wafer. Equivalent circuit analysis, in which all the components are determined by measuring both the electrical and optical characteristics of a three-terminal HPT, shows good agreement with experimental results     

用氧化镉(CdO)为发射区的InGaAsP/InP双异质结晶体管

本文提出和研制了一个新型的InGaAsP/InP双极型晶体管.在单片集成电路中它能与1.55μmInGaAsP/InP双异质结激光器共容而组成一个晶体管-激光器器件.该晶体管的主要特点是采用氧化镉(CdO)薄层作为器件发射区,由InP组成收集区而形成NpN双异质结晶体管.测量结果表明晶体管能双向工作,测得的正向共发射极电流增益为40(V_(CE)=5V,Ic=1mA),反向增益为8(V_(CE)=1.5V,Ic=100μA).文中还给出了h_(fe)—I_c特性和晶体管CdO-InGaAsP发射结的伏安特性.     

Thermal effects on the characteristics of AlGaAs/GaAsheterojunction bipolar transistors using two-dimensional numericalsimulation

Two-dimensional numerical simulations incorporating the spatial distributions of the energy band and temperature were used to study AlGaAs/GaAs heterojunction bipolar transistor characteristics. It was found that the negative differential resistance and the reduction of the base-emitter voltage for a constant base current in the active region are due to thermal effects. The differential current gain and cutoff frequency decrease when the transistor is operated at high power levels. The temperature distribution of the transistor operated in the active region shows a maximum at the collector region right beneath the emitter mesa. When the transistor is operated in the saturation region, the emitter contact region may be at a slightly lower temperature than the heat sink temperature. This thermoelectric cooling effect results from the utilization of the thermodynamically compatible current and energy flow formulations in which the energy band discontinuities are part of the thermoelectric power     

收集区制在半绝缘磷化铟衬底中的InGaAsP/InP异质结双极晶体管

本文提出并成功地试制了一种InP异质结双极型晶体管.其主要特点是利用在半绝缘InP衬底中注硅形成收集区,然后再进行液相外延形成基区和发射区.本结构能有效减少基区一收集区的结电容C_(BC)和寄生电容.避免了薄基区上制作基极欧姆接触时经常发生的基极-收集极之间的短路问题,提高了器件的可靠性结果表明,该器件具有较高的共发射极电流增益(h_(FE)=150～250),并能够双向工作.文章对该结构的优点进行了分析,给出了器件的工艺过程.     

Fully-planar AlGaAs/GaAs HBT's achieved by selective CBE regrowth

This paper describes a novel fully planar AlGaAs/GaAs heterojunction bipolar transistor (HBT) technology using selective chemical beam epitaxy (CBE). Planarization is achieved by a selective regrowth of the base and collector contact layers. This process allows the simultaneous metallization of the emitter, base and collector on top of the device. For the devices with an emitter-base junction area of 2×6 μm² and a base-collector junction area of 14×6 μm², a current gain cut off frequency of 50 GHz and a maximum oscillation frequency of 30 GHz are achieved. The common emitter current gain h_FE is 25 for a collector current density J_c of 2×10⁴ A/cm²     

Importance of electron scattering with coupled plasmon-optical phonon modes in GaAs planar-doped barrier transistors

The GaAs planar-doped barrier (PDB) transistor is an MBE-grown structure which employs two unipolar homo junction barriers. One barrier, the emitter, injects energetic electrons into a thin n-type base region where these electrons are intended to experience negligible energy relaxation and thereby surmount the second (collector) barrier. Maximum common-base current gain or α values of 0.75 have been obtained at 77 K in experimental devices with base widths of 870 Å. Microwave measurements from 2 to 18 GHz on these devices imply a unity common-emitter current gain frequency fTof ∼ 40 GHz. The observed α values in other devices are unfortunately lower than those predicted by recent Monte Carlo simulations, and an unexpectedly strong dependence of α on ambient electron density in the base is noted. These are attributed to the previously overlooked electron scattering with coupled plasmon-optical phonon modes, and to electron-electron scattering. These scattering mechanisms must be included in any accurate model of energetic electron transport in GaAs in regions where the concentration of cooler ambient electrons is above 10¹⁷cm^-3.