Comparative investigation of InP/InGaAs abrupt, setback, and heterostructure-emitter heterojunction bipolar transistors

In this paper, the characteristics of InP/InGaAs abrupt, setback, and heterostructure-emitter heterojunction bipolar transistors (HBTs) are comparatively investigated by twodimensional simulation analysis. In the setback (heterostructure-emitter) HBT, a thin 50 ? undoped In_0.53Ga_0.47As (n-In_0.53Ga_0.47As) layer is inserted between n-InP emitter and p ⁺-InGaAs base layers to lower the energy band at emitter side for decreasing the collector-emitter offset voltage. The simulated results exhibits that the abrupt HBT has the largest current gain, the largest collector-emitter offset voltage, and the smallest unity gain cutoff frequency. While, the setback and heterostructure-emitter HBTs exhibit the smallest current gain and offcet voltage, respectively. Consequentially, the demonstration and comparison of the three-type HBTs provide a promise for design in circuit applications.     

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.     

Ultra-high-speed InP/InGaAs heterojunction bipolar transistors

We report on the microwave performance of InP/In_0.53Ga _0.47As heterojunction bipolar transistors (HBT's) utilizing a carbon-doped base grown by chemical beam epitaxy (CBE). The f_T and f_max of the HBT having two 1.5×10 μm² emitter fingers were 175 GHz and 70 GHz, respectively, at I_C=40 mA and V_CE=1.5 V. To our knowledge, the f _T of this device is the highest of any type of bipolar transistors yet reported. These results indicate the great potential of carbon-doped base InP/InGaAs HBT's for high-speed applications     

Subpicosecond InP/InGaAs heterostructure bipolar transistors

Bipolar transistors with subpicosecond extrinsic delay are discussed. These InP/InGaAs heterostructure transistors show a unity-current-gain cutoff frequency f_$T=165 GHz and maximum oscillation frequency f_MAX=100 GHz at room temperature. The authors model shows that an f_$T beyond 386 GHz is obtainable by further vertical scaling. Ring oscillators implemented with nonthreshold logic (NTL) and transistors having f_MAX=71 GHz show a propagation delay of 14.7 ps and 5.4 mW average power consumption per stage     

High-speed InP/InGaAs heterojunction bipolar transistors

Very-high-performance common-emitter InP/InGaAs single heterojunction bipolar transistors (HBTs) grown by metalorganic molecular beam epitaxy (MOMBE) are reported. They exhibit a maximum oscillation frequency (f_T) of 180 GHz at a current density of 1×10⁵ A/cm². this corresponds to an (R_BC_BC)_eff=f _T/(8πf²_max) delay time of 0.12 ps, which is the smallest value every reported for common-emitter InP/InGaAs HBTs. The devices have 11 μm² total emitter area and exhibit current gain values up to 100 at zero base-collector bias voltage. The breakdown voltage of these devices is high with measured BV_CEO and BV_CEO of 8 and 17 V, respectively     

Selfaligned InGaAs/InP heterostructure bipolar transistors

InGaAs/InP heterostructure bipolar transistors have been realised using a new selfaligned process. Transistor wafers were grown by chemical beam epitaxy. Ideality factors close to unity were measured for emitter-base and collector-base diodes. The resulting devices exhibit nearly constant gain over four orders of magnitude of collector current densities, from j=1.5*10/sup -4/ A/cm/sup 2/ to 1.5 A/cm/sup 2/.<>     

Electrical properties of the InP/InGaAs pnp heterostructure-emitter bipolar transistor

The dc performances of an InP/InGaAs pnp heterostructure-emitter bipolar transistor are investigated by theoretical analysis and experimental results. Though the valence band discontinuity at the InP/InGaAs heterojunction is relatively large, the addition of a heavily-doped as well as thin p ⁺-InGaAs emitter layer between p-InP confinement and n ⁺-InGaAs base layers effectively eliminates the potential spike at emitter-base junction and simultaneously lowers the emitter-collector offset voltage and increases the potential barrier for electrons. Experimentally, a high current gain of 88 and a low offset voltage of 54 mV have been achieved. The text was submitted by the authors in English.     

InP/InGaAs double heterojunction bipolar transistors incorporating carbon-doped bases and superlattice graded base-collector junctions

High performance InP/InGaAs double heterojunction bipolar transistors (DHBTs) incorporating carbon-doped bases and graded base-collector junctions implemented using a short period superlattice were grown by gas source MBE (GSMBE). Base hole concentrations up to 1.6*10/sup 19/ cm/sup -3/ were obtained, using CCl/sub 4/ as the dopant source. Transistors with 2*10 mu m/sup 2/ emitters achieved f/sub t/ and f/sub max/ values up to 76 and 82 GHz, respectively. These devices demonstrate state of the art values of f/sub max/.<>     

InGaAs/InP composite collector heterostructure bipolar transistors

A high speed bipolar transistor with high breakdown voltage BV/sub CEO/ is described. The structure uses a composite collector of InGaAs and InP. A common emitter gain of 65 is obtained with a base doping of 7*10/sup 19/ cm/sup -3/ and a breakdown voltage in excess of 10 V. The f/sub T/=64 GHz was reached at a collector-emitter voltage of 2 V and a current density of 52 kA/cm/sup 2/. The potential of this structure for very high speed applications is demonstrated by the extracted intrinsic transit time of 0.4 ps.<>     

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     

Be diffusion in InGaAs/InP heterojunction bipolar transistors

Classic signatures of Be diffusion were observed in InAlAs/InGaAs HBT's after elevated temperature bias stress, i.e., a positive shift in the Gummel plot, higher collector ideality, and higher offset voltage. An activation energy of 1.57 eV was calculated. Lifetimes of 3.3×106 h and 37000 h were extrapolated for low and high power operation, respectively. In contrast, an InP/InGaAs HBT with a C doped base showed no signatures of C diffusion. The results show that Be diffusion is manageable at lower power. They also support the idea that C is more stable than Be in this material system     

On the storage time of InGaAs/InP bipolar transistors

The collector storage time was measured for InGaAs/InP bipolar transistors. For the evaluation, the transistors were driven into deep saturation choosing a test condition with no reverse base current. Devices comprising a homojunction- and a modified wide-gap-collector structure, respectively, were compared. For the latter device structure a marked reduction of the storage time by a factor of 10 was found.     

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.     

Breakdown-speed considerations in InP/InGaAs single- anddouble-heterostructure bipolar transistors

The breakdown and speed characteristics of InP/InGaAs single and double HBTs are presented. Temperature-dependent two- and three-terminal measurements suggest that avalanche impact ionization is the dominant breakdown mechanism in InGaAs collector HBTs. Monte Carlo techniques and 1D drift-diffusion modeling are used for speed and breakdown simulation, respectively. Special doping profiles are evaluated for improving the breakdown-speed characteristics of single HBTs (SHBTs) with conventional uniformly doped InGaAs collectors. Double HBTs (DHBTs) outperform all SHBTs in terms of speed-breakdown tradeoffs as long as they use graded base-collector junctions or they operate under sufficiently high collector-emitter voltage conditions. A cutoff frequency of 200 GHz was found to be feasible with graded DHBTs, and breakdown voltages up to 4.6 V were evaluated with a 3000-Å-thick collector. Nongraded DHBTs can be optimized to perform better in terms of speed-breakdown tradeoffs provided that a high collector doping is used     

InP/InGaAs double heterostructure bipolar transistors grown by MBE

Double heterostructure bipolar transistors have been fabricated on InP/InGaAs MBE material. Current gains of up to 80 have been observed in the emitter-up configuration. The devices were fabricated using two diffusion techniques and selective etching to contact the base.     

InP/InGaAs heterojunction bipolar transistors with different g-bridge structures

Several μ-bridge structures for InP-based heterojunction bipolar transistors (HBTs) are reported. The radio frequency measurement results of these InP HBTs are compared with each other. The comparison shows that μ-bridge structures reduce the parasites and double μ-bridge structures have a better effect. Due to the utilization of the double μ-bridges, both the cutoff frequency f_T and also the maximum oscillation frequency f_(max) of the 2×12.5 μm~2 InP/InGaAs HBT reach nearly 160 GHz. The results also show that the μ-bridge has a better effect in increasing the high frequency performance of a narrow emitter InP HBT.     

Comparative study of InP/InGaAs double heterojunction bipolar transistors with InGaAsP spacer at base-collector junction

In this article, the influence of InGaAsP spacers inserted at base-collector (B-C) junction in the InP/In_0.53Ga_0.47As double heterojunction bipolar transistors is demonstrated by two-dimensional semiconductor simulation. Due to the addition of an InGaAsP spacer layer, two small potential spikes are formed at B-C junction and the current blocking effect is reduced. The results exhibit that the maximum current gain increases from 30 to 374 (375) as the thickness of InGaAsP spacer layer varies from 0 to 100 Å (300 Å). On the other hand, the device with a thicker spacer layer (300 Å) could effectively improve the knee effect of the current-voltage curves as compared the other devices. In addition, the collector-emitter offset voltages less than 10 mV are observed in the three devices.     

Predicted performance of high-speed integrated-injection logicusing InGaAs/InP heterojunction bipolar transistors

By the use of analytical expressions and SPICE simulation, the switching performance of integrated injection logic (I²L) using heterojunction bipolar transistors (HBTs) has been investigated. A proposed inverter configuration using InP/InGaAs HBTs which avoids saturation in the p-n-p injector has predicted propagation delays of 16 ps at only 3-mW power dissipation. Transient response analysis illustrates the importance of reducing parasitic resistances in the structure. Ring oscillator simulations indicate that switching speeds approaching those of emitter-coupled logic but with advantages in high density and low power are possible     

High-speed InGaAs(P)/InP double-heterostructure bipolar transistors

Double-heterostructure InGaAs(P)/InP bipolar transistors ranging in emitter size from 5 × 10 to 100 × 150 µm²have been fabricated using a non-self-aligned technology. These transistors exhibit current gains as high as 275 independent of emitter perimeter-to-area ratio. The best frequency of unity current gain was measured in the smallest devices to be 18 GHz. The high-frequency operation was mainly limited by the emitter charging time.     

Millimetre-wave InP/InGaAs heterojunction bipolar transistors witha subpicosecond extrinsic delay time

We report the microwave characteristics of InP/InGaAs heterojunction bipolar transistors (HBTs) using a carbon-doped base grown by chemical beam epitaxy (CBE). An extrinsic delay time of 0.856 ps was achieved by nonequilibrium transport in a very thin base layer and extremely small emitter parasitic resistance through the use of silicon δ-doping in the emitter ohmic contact layer. To our knowledge, this is the shortest extrinsic delay time of any bipolar transistors reported. This result indicates the great potential of InP/InGaAs HBTs for applications requiring a very large bandwidth