Carbon-doped Base Research Articles

InP/InGaAs/InP DHBT structures with high carbon-doped base grown by gas source molecular beam epitaxy

A new InP/InGaAs/InP DHBT structure with high carbon (C)-doped base was optimized and grown successfully by gas source molecular beam epitaxy (GSMBE) in this work. The C-doping concentration is 3×1019cm−3 with carrier mobility of 66.3cm2/Vs. Characteristics of C-doped InGaAs materials were investigated. High quality InP/InGaAs/InP DHBT structural materials were obtained. The InP/InGaAs/InP DHBT device with emitter area of 100×100μm2 was fabricated. The open base breakdown voltage (VBCEO) of 4.2V and current gain of 60 at VCE of 3.0V were achieved. All these results prove the material is suitable for DHBT device fabrication.

InP/InAlGaAs light-emitting transistors and transistor lasers with a carbon-doped base layer

Characteristics of InP/InAlGaAs light-emitting transistors (LETs) and transistor lasers (TLs) using carbon (C) for p-type doping of the base region were investigated. The N-InP/p-In0.52(Al0.4Ga0.6)0.48As/N-In0.52Al0.48As LETs show a current gain of 0.22 and light emission at wavelength of λ ∼ 1610 nm. The low current gain is attributed to the short minority carrier lifetime in the C-doped base with a quantum well. The TL demonstrates continuous-wave operation at −190 °C with a threshold current of IB = 35 mA. By comparing the optical output characteristics of the TL and a laser diode with similar structure, it is suggested that the low differential quantum efficiency and the high threshold current density in the TL is related to the strong inter-valence band absorption in the heavily doped base layer.

Comparative Study on Reliability of InP/InGaAs Heterojunction Bipolar Transistors with Highly Zn- and C-Doped Base Layers

AbstractThe reliability of InP/InGaAs heterojunction bipolar transistors (HBTs) with highly carbon-doped and zinc-doped InGaAs base layers grown by metal-organic vapor phase epitaxy has been investigated. The Raman spectroscopy reveals that the post-growth annealing for the carbon-doped InGaAs base improves the crystallinity to become as good as that of the zinc-doped InGaAs base. However, the photoluminescence intensity remains lower than that of the zinc-doped InGaAs even after the post-growth annealing. The current gains of the carbon- and zinc-doped base InP/InGaAs HBTs are 63 and 75, respectively, and they are affected by the base crystallinity. After the 15-min current stress test, the current gains decreased by 40 and 3% from the initial current gains for zinc- and carbon-doped base HBTs, respectively, are observed. These results indicate that the carbon-doped base HBT is much more reliable than that of zinc-doped base HBT, though it has a lower current gain.

High-Gain Arsenic-Rich n-p-n InP/GaAsSb DHBTs With $F_{T} ≫ \hbox{420}\ \hbox{GHz}$

Type-II n-p-n InP/GaAsSb/InP double heterostructure bipolar transistors (DHBTs) that are fabricated by optical lithography with a 0.6 times 5 mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> emitter on a 20-nm compositionally uniform GaAsSb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> , carbon-doped base with x = 0.60 and a 75-nm InP collector show current-gain cutoff frequencies as high as 423 GHz at 10 mA/mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and feature a BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CEO</sub> = 4 V. The pseudomorphic As-rich InP/GaAsSb DHBTs feature a high maximum dc current gain of > 160, owing to the reduction of the type-II conduction band discontinuity DeltaE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> and the associated recombination at the InP/GaAsSb emitter-base interface. This brief demonstrates that the InP/GaAsSb DHBT technology can combine high gain, wide bandwidths, high-current drivability, and structural simplicity.

Heavily carbon-doped p-type InGaAs grown by gas source molecular beam epitaxy for application to heterojunction bipolar transistors

The growth and characteristics of ultrahigh carbon-doped p-type InGaAs lattice matched to InP by gas source molecular beam epitaxy (GSMBE) using carbon tetrabromide (CBr 4) as a doping source was investigated. The effects of growth temperature, group V supply pressure and CBr 4 supply pressure on the composition, hole mobility and concentration of carbon-doped InGaAs were studied. The dependence of hydrogen passivation effect on different AsH 3 supply pressure and different growth temperature were researched. Ultrahigh net hole concentration and room-temperature mobility of 1×10 20 cm −3 and 45 cm 2/V s, respectively, were achieved without any postgrowth annealing. Mobility of the ultrahigh carbon-doped InGaAs using CBr 4 compared favorably to those of CBE grown carbon-doped InGaAs using CBr 4 and molecular beam epitaxy grown beryllium (Be)-doped InGaAs grown at low temperature. The highly carbon-doped InGaAs layers grown by GSMBE using CBr 4 as a doping source were used for the growth of high performance, highly carbon-doped base InP/InGaAs heterojunction bipolar transistor epitaxial layer structures.

Characterization of InP/InGaAs Heterojunction Bipolar Transistors with Carbon-Doped Base Layers Grown by Metal-Organic Chemical Vapor Deposition and Molecular Beam Epitaxy

We characterized InP/InGaAs heterojunction bipolar transistors (HBTs) with carbon-doped InGaAs base layers grown by metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). Since HBTs grown using these techniques require different processing steps, resulting in different types of process-related damage, we analyzed the bulk and periphery components of DC characteristics to clarify the effects of the crystal growth and process techniques on device characteristics separately. The MBE-grown HBTs were found to have an advantage over the MOCVD-grown HBTs, because they do not require harmful high-temperature annealing during processing steps. On the other hand, it was also shown that the MOCVD-grown HBTs have a significantly lower base recombination rate than the MBE-grown HBTs, making MOCVD a suitable method of growing InP HBTs that do not require annealing, such as that with a GaAsSb base.

High-performance InP/GaAsSb/InP DHBTs grown by MOCVD on 100 mm InP substrates using PH 3 and AsH 3

High-performance MOCVD-grown N-p-N InP/GaAsSb/InP DHBTs based on epitaxial layers deposited on 100 mm InP substrates are reported. The transistors feature the first nearly ideal emitter/base junction characteristics reported for material grown using AsH 3 and PH 3 hydride precursors, a DC current gain β=30–40, and a peak cutoff frequency f T=245 GHz for a 0.5×12 μm 2 emitter fabricated on a 250 Å lattice-matched carbon-doped base. We discuss layer composition and thickness uniformity, C-doping efficiency as determined by the comparison of SIMS and Hall effect data on bulk GaAs 0.5Sb 0.5 layers, as well as provide SIMS and TEM data for the transistor layers (including a lattice image of the interface between GaAsSb and InP). To our knowledge, the present article provides the first detailed characterization of high-speed InP/GaAsSb/InP DHBTs fabricated on industrially grown epitaxial layers.

InGaAs–InP Mesa DHBTs With Simultaneously High&amp;lt;tex&amp;gt;$f_tau$&amp;lt;/tex&amp;gt;and&amp;lt;tex&amp;gt;$f_max$&amp;lt;/tex&amp;gt;and Low&amp;lt;tex&amp;gt;$C_rm cb/I_c$&amp;lt;/tex&amp;gt;Ratio

We report an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370-GHz f/sub /spl tau// and 459-GHz f/sub max/, which is to our knowledge the highest f/sub /spl tau// reported for a mesa InP DHBT-as well as the highest simultaneous f/sub /spl tau// and f/sub max/ for any mesa HBT. The collector semiconductor was undercut to reduce the base-collector capacitance, producing a C/sub cb//I/sub c/ ratio of 0.28 ps/V at V/sub cb/=0.5 V. The V/sub BR,CEO/ is 5.6 V and the devices fail thermally only at >18 mW//spl mu/m/sup 2/, allowing dc bias from J/sub e/=4.8 mA//spl mu/m/sup 2/ at V/sub ce/=3.9 V to J/sub e/=12.5 mA//spl mu/m/sup 2/ at V/sub ce/=1.5 V. The device employs a 30 nm carbon-doped InGaAs base with graded base doping, and an InGaAs-InAlAs superlattice grade in the base-collector junction that contributes to a total depleted collector thickness of 150 nm.

High-performance InP/GaAsSb/InP DHBTs grown by MOCVD on 100mm InP substrates using PH3 and AsH3

High-performance MOCVD-grown N-p-N InP/GaAsSb/InP DHBTs based on epitaxial layers deposited on 100 mm InP substrates are reported. The transistors feature the first nearly ideal emitter/base junction characteristics reported for material grown using AsH3 and PH3 hydride precursors, a DC current gain β=30–40, and a peak cutoff frequency fT=245 GHz for a 0.5×12 μm2 emitter fabricated on a 250 Å lattice-matched carbon-doped base. We discuss layer composition and thickness uniformity, C-doping efficiency as determined by the comparison of SIMS and Hall effect data on bulk GaAs0.5Sb0.5 layers, as well as provide SIMS and TEM data for the transistor layers (including a lattice image of the interface between GaAsSb and InP). To our knowledge, the present article provides the first detailed characterization of high-speed InP/GaAsSb/InP DHBTs fabricated on industrially grown epitaxial layers.

Study of direct current characteristics of carbon-doped GaInP/GaAs heterojunction bipolar transistor grown by solid source molecular beam epitaxy

This article reports the dc characteristics of a GaInP/GaAs heterojunction bipolar transistor (HBT) with carbon-doped GaAs base layer grown by solid source molecular beam epitaxy using carbon tetrabromide (CBr4) as p-type dopant precursor. Hydrofluoric acid (HF) was used to passivate the GaInP/GaAs HBTs. At base bias voltages below 0.9 V in the Gummel plot, the base current of large area devices after HF passivation, was greatly reduced indicating that the extrinsic base surface recombination current was significantly reduced. After HF passivation, detailed dc characterization of the device performance within the temperature range of 300–380 K was carried out, and the carrier transport properties were investigated. The base current and collector current ideality factors at 300 K were 1.12 and 1.01, respectively. This indicates that a space charge region recombination current is insignificant in the base. From the temperature dependent Gummel plot, the activation energies of the collector current and base current were obtained. For the collector current, the activation energy is 1.4 eV, which is close to the band gap of the GaAs base. This indicates that the collector current is determined by the drift-diffusion process. For the base current, the activation energy is also 1.4 eV, indicating that band-to-band recombination plays a dominant role in the base current. No trap-related recombination was observed in the base and collector currents, which further indicates the good base material quality in the HBT structure. The current gain versus collector current characteristics at different temperatures were also investigated and analyzed.

Effects of annealing on the hydrogen concentration and the performance of InGaP/InGaAsN/GaAs heterojunction bipolar transistors

The effects of rapid thermal annealing (RTA) on InGaP/InGaAsN heterojunction bipolar transistors (HBTs) with a carbon-doped base have been studied. The hydrogen and nitrogen concentrations in the base, as well as the direct current (DC) and radio frequency (RF) device performance, were studied as a function of the annealing temperature. A 30-sec anneal at 650°C and 700°C under N2 ambient effectively eliminates hydrogen from the base. As the annealing temperature is increased, the base sheet resistance decreases, and the corresponding maximum frequency of oscillation increases. For all annealing temperatures studied, we found degradation in the DC gain, presumably caused by the increase of nitrogen concentration in the base region.

Wideband DHBTs using a graded carbon-doped InGaAs base

We report an InP/InGaAs/InP double heterojunction bipolar transistor (DHBT), fabricated using a mesa structure, exhibiting 282 GHz f/sub /spl tau// and 400 GHz f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> . The DHBT employs a 30 nm InGaAs base with carbon doping graded from 8/spl middot/10/sup 19//cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> to 5/spl middot/10/sup 19//cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , an InP collector, and an InGaAs/InAlAs base-collector superlattice grade, with a total 217 nm collector depletion layer thickness. The low base sheet (580 /spl Omega/) and contact (<10 /spl Omega/-μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) resistivities are in part responsible for the high f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> observed.

Dependence of burn-in effect on thermal annealing of the GaAs:C base layer in GaInP heterojunction bipolar transistors

We investigate in situ thermal annealing of the carbon-doped GaAs base layer in GaInP/GaAs heterojunction bipolar transistors grown by metalorganic chemical vapor deposition in order to eliminate hydrogen incorporation. The influence of the anneal on the carrier transport properties and on the burn-in effect is studied. Results show that the anneal reduces the burn-in effect due to an increase in the emitter minority carrier diffusion length which is caused by passivation of H+ recombination centers in the GaInP emitter layer. However, the anneal also degrades the base minority carrier diffusion length leading to a reduction in the current gain.

Elevated Temperature Characteristics of Carbon-Doped GaInP/GaAs Heterojunction Bipolar Transistor Grown by Solid Source Molecular Beam Epitaxy

ABSTRACTThis paper reports the characteristics of GaInP/GaAs heterojunction bipolar transistor (HBT) with carbon-doped GaAs base layer grown by solid source molecular beam epitaxy (SSMBE) using carbon tetrabromide (CBr4) as p-type dopant precursor. Hydrofluoric acid (HF) was used to passivate the GaInP/GaAs HBTs. At base bias voltages below 0.8V in the Gummel plot, the base current of large-area devices after HF treatment was greatly reduced. This indicates that the extrinsic base surface recombination current was greatly reduced. After HF treatment, detailed DC characterization of the device performance from 300K to 380K was carried out and the carrier transport properties were investigated. The base current and collector current ideality factors at 300K were 1.12 and 1.01, respectively. This indicates that the space- charge region recombination current in the base is insignificant. From the temperature- dependent Gummel plot, the activation energies of collector current and base current were obtained. For the collector current, the activation energy is 1.4eV, which is close to the bandgap of the GaAs base. This indicates that the collector current is determined by the drift-diffusion process, in which an energy barrier of the same magnitude as the base bandgap is to be overcome by electrons before they reach the collector. For the base current, the activation energy is also 1.4eV, which is close to the bandgap of GaAs, indicating that band-to-band recombination plays a dominant role in the base current. No trap-related recombination was observed for the base and collector currents, which further indicates the high quality carbon-doped GaAs base material for the HBT structures.

Comparison of DC and high-frequency performance of zinc-doped and carbon-doped InP/InGaAs HBTs grown by metalorganic chemical vapor deposition

Zinc and carbon-doped InP/InGaAs heterojunction bipolar transistors (HBTs) with the same design were grown by metalorganic chemical vapor deposition (MOCVD). DC current gain values of 36 and 16 were measured for zinc and carbon-doped HBTs, respectively, and carrier lifetimes were measured by time-resolved photoluminescence to explain the difference. Transmission line model (TLM) analysis of carbon-doped base layers showed excellent sheet-resistance (828 /spl Omega///spl square/ for 600 A base), indicating successful growth of highly carbon-doped base (2/spl times/10/sup 19/ cm/sup -3/). The reasons for larger contact resistance of carbon than zinc-doped base despite its low sheet resistance were analyzed. f/sub T/ and f/sub max/ of 72 and 109 GHz were measured for zinc-doped HBTs, while 70-GHz f/sub T/ and 102 GHz f/sub max/ were measured for carbon-doped devices. While the best performance was similar for the two HBTs, the associated biasing current densities were much different between zinc (4.0/spl times/10/sup 4/ A/cm/sup 2/) and carbon-doped HBTs (2.0/spl times/10/sup 5/ A/cm/sup 2/). The bias-dependant high-frequency performance of the HBTs was measured and analyzed to explain the discrepancy.

Growth of ultrahigh carbon-doped InGaAs and its application to InP/InGaAs(C) HBTs

Growth of ultrahigh carbon-doped p-type InGaAs lattice matched to InP by chemical beam epitaxy (CBE) using carbon tetrabromide (CBr/sub 4/) as a doping source was investigated. Effects of growth temperature, group V supply pressure, and CBr/sub 4/ supply pressure on growth rate, composition, mobility, and hole concentration of carbon-doped InGaAs were studied. Ultrahigh net hole concentration and room-temperature mobility of 2 /spl times/ 10/sup 20//cm/sup 3/ and 33 cm/sup 2//V/spl middot/sec, respectively, were achieved. Mobility of the ultrahigh carbon-doped InGaAs using CBr/sub 4/ compared favorably to those of CBE grown carbon-doped InGaAs using carbon tetrachloride (CCl/sub 4/) and molecular beam epitaxy grown beryllium (Be)-doped InGaAs grown at low temperature. The highly carbon-doped InGaAs layers grown by CBE using CBr/sub 4/ as a doping source showed a negligible hydrogen passivation effect and were used for the growth of high-performance, highly carbon-doped base InP/InGaAs heterojunction bipolar transistor epitaxial layer structures.

Properties of carbon-doped GaN

The properties of carbon-doped GaN epilayers grown by molecular-beam epitaxy have been studied by temperature-dependent resistivity, Hall-effect measurements, x-ray diffraction, and by photoluminescence spectroscopy. Carbon doping was found to render the GaN layers highly resistive (&amp;gt;108 Ω cm) and quench the band edge excitonic emissions. Yellow luminescence is still present in carbon-doped GaN layers. The highly resistive state is interpreted as being caused by direct compensation by the carbon acceptors and by the consequently enhanced potential barrier at the subgrain boundaries. Evidence of dislocations joining to form potential barriers along the subgrain boundaries was observed in photoassisted wet etching experiments on electrically conducting GaN layers. GaN films grown on insulating carbon-doped base layers are of excellent transport and optical properties.

Minority carrier lifetime degradation in carbon-doped base of InGaP/GaAs heterojunction bipolar transistors grown by low-pressure metalorganic chemical vapor deposition

The effect of intermediate temperature annealing on the carbon-doped base region of InGaP/GaAs heterojunction bipolar transistors (HBTs) was studied. This work shows that the minority carrier lifetime in the samples doped at 5.5×1019 cm−3 decreases upon annealing at only 600 °C. Magnetotransport measurements were performed to obtain the minority carrier mobility, with which the minority carrier lifetime was extracted. The decrease in the direct current (dc) current gain upon annealing is attributed to the increase in the base bulk recombination. The correlation between the dc current gain and the magnetotransport measurements indicates that the annealing increases the carbon-related defects in the GaAs base, decreases the minority carrier lifetime in the carbon-doped base, and degrades the dc current gain of the InGaP/GaAs HBTs. These results are very important to the growth and postgrowth processing of InGaP/GaAs HBTs.

Investigation of carbon-doped base materials grown by CBE for Al-free InP HBTs

InGaAs/InP heterojunction bipolar transistors with a carbon-doped base are shown to have lower gain that those with a Be-doped base. In order to keep advantage of the low diffusivity of the carbon dopant, alternative carbon-doped materials have been tested as the base material. A quaternary InGaAsP alloy with a lower band gap than InGaAs to reduce Auger recombination proved to be unsatisfactory, because of low doping (<2×10 19 cm −3) and dramatically lower electron lifetime than in InGaAs. The compositionally graded base proved to be an attractive solution, allowing significantly improved gain in HBTs, and leading to some advantageous side effects, such as higher doping level, constant gain over large current range, and higher frequencies.

Optimization of emitter cap growth conditions for InGaP/GaAs HBTs with high current gain by LP-MOCVD

The effect of emitter cap growth conditions on the common-emitter current gain of InGaP/GaAs HBTs, grown by LP-MOCVD, has been studied. This work shows that the material quality of a carbon-doped base is highly dependent on the emitter cap growth. The emitter cap growth effectively serves as a source of thermal stress. This stress on the base during the emitter and cap growth causes the formation of carbon-related defects in the base that increase the base recombination and reduces the current gain. Atomic force microscopy is used to identify these carbon-related defects. Gain improvements of about 40% have been achieved by optimizing the emitter cap growth conditions to reduce the thermal stress.