InP/InGaAs heterojunction bipolar transistors grown by gas-sourcemolecular beam epitaxy with carbon-doped base

The first N-p-n InP/InGaAs heterojunction bipolar transistors (HBTs) with p-type carbon doping in InGaAs are reported. P-type carbon doping in the InGaAs base has been achieved by gas-source molecular beam epitaxy (GSMBE) using carbon tetrachloride (CCl₄) as the dopant source. The resulting hole concentration in the base was 1×10¹⁹ cm^-3. HBTs fabricated using material from this growth method display good I-V characteristics with DC current gain above 500. This verifies the ability to use carbon doping to make a heavily p-type InGaAs base of an N-p-n HBT     

A comparative study of metamorphic InP/InGaAs double heterojunction bipolar transistors with InP and InAIP buffer layers grown by molecular beam epitaxy

We present a comparison of material quality and device performance of metamorphic InGaAs/InP heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy (MBE) on GaAs substrates with two different types of buffer layers (direct InP and graded InAlP buffers). The results show that the active layer of InP-MHBT has more than one order of magnitude more defects than that of the InAlP-MHBT. The InAlP-MHBTs show excellent direct current (DC) performance. Low DC current gain and a high base junction ideality factor from the InP-MHBT are possibly due to a large number of electrically active dislocations in the HBT active layers, which is consistent with a large number of defects observed by cross-sectional transmission electron microscopy (TEM) and rough surface morphology observed by atomic force microscopy (AFM).     

High-performance carbon-doped base GaAs/AlGaAs heterojunction bipolar transistor grown by MOCVD

High-performance HBTs with a carbon-doped base layer (p=4*10/sup 19/ cm/sup -3/) are reported. The use of carbon as a p-type dopant allows the emitter-base p-n junction to be accurately positioned relative to the heterojunction, and the MOCVD growth method ensures consistency and uniformity of the wafer epitaxial structure. Microwave HBTs with current gains h/sub FE/=50 and f/sub T/ and f/sub max/ values of 42 GHz and 117 GHz, respectively, are reported.<>     

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     

Atomic layer epitaxy grown heterojunction bipolar transistor havinga carbon-doped base

The fabrication of a GaAs/AlGaAs heterojunction bipolar transistor (HBT) having a carbon-doped base is reported. The low diffusion coefficient of carbon makes it attractive for HBT applications since it will prevent out diffusion. The base was grown by atomic layer epitaxy (ALE), from a TMG (trimethylgallium) source that allowed the incorporation of carbon into the layer from the partially related TMG metal carbide. HBTs with common-emitter current gains of 100 were obtained at current densities of 1300 A-cm^-2     

AlGaAs/InGaAs/GaAs strained-layer heterojunction bipolar transistors by molecular beam epitaxy

The growth and characteristics of the first AlGaAs/InGaAs/GaAs HBTs are reported. Layers with up to 10% indium content appeared to be free of misfit dislocations, and resulted in HBTs with good I/V characteristics which scaled with In content according to theory.     

InGaAs/lnP heterojunction bipolar transistor grown by all-solidsource molecular beam epitaxy

State-of-the-art InGaAs/InP heterojunction bipolar transistors were grown by all-solid source molecular beam epitaxy. Fabricated transistors showed cutoff frequencies of >100 GHz with an emitter area of 1.5×5 μm². Together with recent studies. These results demonstrate that the valved cracker technique is a very competitive nontoxic growth method     

Silicon-germanium base heterojunction bipolar transistors bymolecular beam epitaxy

The devices were fabricated using molecular-beam epitaxy (MBE), low-temperature processing, and germanium concentrations of 0, 6%, and 12%. The transistors demonstrate current gain, and show the expected increase in collector current as a result of reduced bandgap due to Ge incorporation in the base. For a 1000-Å base device containing 12% Ge, a six-times increase in collector current was measured at room temperature, while a 1000-times increase was observed to 90 K. The temperature dependence of the collector current of the Si_0.88Ge_0.12 base transistor is consistent with a bandgap shrinkage in the base of 50 meV. For the homojunction transistors, base widths as thin as 800 Å were grown, corresponding to a neutral base width of no more than 400 Å     

Heavily doped base GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy

The first demonstration of a GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy is reported. A common-emitter current gain of 30 at a current density of 110 A/cm/sup 2/ is obtained for a beryllium base doping as high as 8*10/sup 19/ cm/sup -3/. The base sheet resistance of 140 Omega / Square Operator is among the lowest reported values.<>     

InP/InGaAsP/InGaAs avalanche photodiodes grown by chemical beam epitaxy

InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions (SAGM-APD's) have been fabricated from wafers grown by chemical beam epitaxy (CBE). These APD's exhibit low dark current (<25 nA at 90 percent of breakdown), low capacitance (≈0.2 pF), and good responsivity (0.75 A/ W at 1.3 µm). The pulse response, which is relatively independent of avalanche gain, is characterized by rise and fall times of approximately 1.4 ns.     

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/.<>     

AlGaAs/Ge/GaAs heterojunction bipolar transistors grown bymolecular beam epitaxy

An N-Al_0.22Ga_0.78As emitter, p-Ge base, and n-GaAs collector (AlGaAs/Ge/GaAs) heterojunction bipolar transistor (HBT) in the emitter-up configuration grown by molecular beam epitaxy is discussed. Devices exhibited common-emitter current gains of as high as 300 at a collector current density of 2000 A/cm² and a collector voltage of 4 V. As the device area is reduced from 50×50 to 10×40 μm, the current gain did not show significant changes, suggesting a low surface recombination velocity in the Ge 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.     

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     

Heterojunction bipolar transistors with SiGe base grown bymolecular beam epitaxy

High-quality SiGe heterojunction bipolar transistors (HBTs) have been fabricated using material grown by molecular beam epitaxy (MBE). The height of parasitic barriers in the conduction band varied over the wafer, and the influence of these barriers on controller current, early voltage, and cutoff frequency were studied by experiments and simulations. Temperature-dependent measurements were performed to study the influence of the barriers on the effective bandgap narrowing in the base and to obtain an expression for the collector-current enhancement. From temperature-dependent measurements, the authors demonstrate that the collector-current enhancement of the HBTs can be described by a single exponential function with a temperature-independent prefactor     

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.     

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.     

Low-base-resistance InP/InGaAs heterojunction bipolar transistors with a compositionally graded-base structure

To reduce base resistance of an InP/InGaAs heterojunction bipolar transistor grown by gas-source molecular beam epitaxy, the doping characteristics of carbon-doped InGaAs and the dependence of doping concentration on current gain were investigated. Using a thicker graded base was found to increase current gain significantly, resulting in increased doping level in the InGaAs: C-base layer. In particular, an 80-nm-thick graded base produces a base sheet resistance of 285 Ω/sq and maintains a practically useful current gain of 23 and a high cut-off frequency of 139 GHz.     

Self-aligned InAlAs/InGaAs heterojunction bipolar transistor with aburied subcollector grown by selective epitaxy

We report the first microwave characterization of an In_0.52 Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistor (HBT) with a buried InGaAs subcollector grown by selective epitaxy. The study compares two HBT's having identical 2×10 μm² self-aligned emitter fingers but different subcollectors. Improvement in microwave performance of the selectively-grown HBT over the conventional HBT was observed due to the reduced parasitic base-collector capacitance achieved by incorporating the selectively-grown buried subcollector