(In,Ga)As/InP n-p-n heterojunction bipolar transistors grown by liquid phase epitaxy with high DC current gain

Experimental results on heterojunction bipolar transistors made in liquid phase epitaxial (In,Ga)As and InP layers on InP substrates are described. The (In,Ga)As base layer was doped with manganese during growth and contacts were made to it by beryllium ion implantation. The maximum measured dc current gain β of these devices was in excess of 500. These devices also demonstrate for the first time in an InP-based system, the inverted emitter-down heterojunction transistor structure with a base contact, which yields a minimized collector-base junction area and should significantly improve high-frequency performance.     

Digital integrated circuit using GaInAs/InP heterojunction bipolar transistors

A divider circuit using GaInAs/InP heterojunction bipolar transistors is reported for the first time. This is the first monolithic digital integrated circuit using these devices. The divider has been clocked at 5 GHz, which is the fastest toggle rate for a bipolar circuit on InP.<>     

GaAs/AlGaAs heterojunction bipolar transistors for integrated circuit applications

Molecular-beam epitaxy (MBE) and ion implantation were used to fabricate GaAs/AlGaAs heterojunction bipolar transistors with buried wide bandgap emitters. Inverted-mode current gains of ∼ 100 were obtained, demonstrating the feasibility of this technology for I²L types of digital integrated circuits.     

Required grading length to eliminate the heterojunction spike in npn In0.52Al0.48As/In0.53Ga0.47As/InP bipolar transistors

Energy-band diagrams have been studied for n-In0.52Al0.48As/p-In0.53Ga0.47As heterojunctions employing different compositional gradings for heterojunction bipolar transistor applications, and the minimum grading widths were calculated for eliminating the conduction-band spike barrier.     

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     

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     

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     

Modeling and characterization for high-speed GaAlAs-GaAs n-p-n heterojunction bipolar transistors

A numerical one-dimensional model is employed to predict dc and switching characteristics for n-p-n type GaAlAs-GaAs transistors, including heteroemitter-homocollector and heteroemitter-heterocollector junction structure, where four kinds of doping profiles are considered. Also, Si and GaAs homojunction transistors are referred to for comparison. Switching performance is discussed for a single unit case, with and without a base resistance, and for a DCTL-type two-stage inverter case, including the delay time dependence on fanout.     

GaAs/(Ga,Al)As heterojunction bipolar transistors with buried oxygen-implanted isolation layers

A simple self-aligned technique using oxygen implants to reduce the extrinsic base-collector capacitance in GaAs/(Ga,Al)As heterojunction bipolar transistors (HBT's) is described. This technique has been used to achieve nonthreshold logic ring-oscillators with propagation delays down to 30 ps per gate, the lowest reported to date for any bipolar transistor circuit.     

Thermal characteristics of InP, InAlAs, and AlGaAsSb metamorphic buffer layers used in In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors grown on GaAs substrates

In_0.52Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistors (HBTs) were grown metamorphically on GaAs substrates by molecular beam epitaxy. In these growths, InAlAs, AlGaAsSb, and InP metamorphic buffer layers were investigated. The InAlAs and AlGaAsSb buffer layers had linear compositional grading while the InP buffer layer used direct binary deposition. The transistors grown on these three layers showed similar characteristics. Bulk thermal conductivities of 10.5, 8.4, and 16.1 W/m K were measured for the InAlAs, AlGaAsSb, and InP buffer layers, as compared to the 69 W/m K bulk thermal conductivity of bulk InP. Calculations of the resulting HBT junction temperature strongly suggest that InP metamorphic buffer layers should be employed for metamorphic HBTs operating at high power densities.     

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     

Surface passivation of lnP/ln0.53Ga0.47As heterojunction bipolar transistors for opto-electronic integration

We report for the first time, a surface passivation technique for InP/In_0.53Ga_0.47As heterojunction bipolar transistors that is suitable for optoelectronic integrated circuits. The combination of buffered hydrofluoric acid with high temperature annealing of the surface causes significant increase of the gain at low input currents. Using this technique, transistors were integrated with photodetectors and other optoelectronic devices and had current gains as high as 400 even at nanoampere base currents.     

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.     

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.     

(GaAl)As/GaAs heterojunction bipolar transistors with graded composition in the base

The first fabrication and high-speed operation of a three-terminal (AlGa)As/GaAs heterojunction bipolar transistor with graded bandgap base is reported. Cutoff frequencies up to 16 GHz have been achieved in devices fabricated from material made by molecular beam epitaxy. This work demonstrates the feasibility of using a graded (AlGa)As base to enhance the speed of heterojunction bipolar transistors.     

Temperature dependence of breakdown and avalanche multiplication in In/sub 0.53/Ga/sub 0.47/As diodes and heterojunction bipolar transistors

The avalanche multiplication and impact ionization coefficients in In/sub 0.53/Ga/sub 0.47/As p-i-n and n-i-p diodes over a range of temperature from 20-400 K were measured and shown to have negative temperature dependence. This is contrary to the positive temperature dependence of the breakdown voltage measured on InP/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistors (HBTs) in this and previous works. It is shown that the collector-base dark current and current gain can be the overriding influence on the temperature dependence of breakdown in InP/In/sub 0.53/Ga/sub 0.47/As HBTs and could explain previous anomalous interpretations from the latter.     

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     

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