Μm2 Emitter Area Research Articles

In0.3Ga0.7As heterojunction bipolar transistor grown on GeSi substrate for high-frequency application

We report an In0.3Ga0.7As HBT device grown on a 200 mm Si wafer using GeSi as virtual starting substrate and InAlAs as the compositionally graded buffer layer from GaAs to In0.3Ga0.7As lattice constant. A DC gain, emitter-base, and base-collector ideality factors of 10, 1.43, and 1.56, respectively, are obtained for a device with an emitter area of 40 × 50 μm2. Small-signal simulation of an In0.3Ga0.7As HBT device with 2 × 8 μm2 emitter area shows that current gain cutoff frequency (fT) and maximum cut-off frequency (fMax), of 50 GHz and 220 GHz, respectively, can be achieved with base doping and layer thickness of 2 × 1018cm−3 and 30 nm, respectively.

GaAsSb-Based DHBTs With a Reduced Base Access Distance and $f_{\mathrm {T}}/f_{\mathrm {MAX}}=$ 503/780 GHz

We report InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with simultaneous current and power gain cutoff frequencies of f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> /f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> = 503/780 GHz. Devices with a 0.2 × 4.4 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> emitter area feature a peak DC current gain β = 17 and a common-emitter breakdown voltage BVCEO = 4.1 V. To the best of our knowledge, the present transistors are the first GaAsSb-based DHBTs to feature f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> > 750 GHz. The progress in RF performance is enabled by a reduction of the base access resistance and base-collector capacitance achieved via an improved self-aligned emitter etching procedure.

In situ integrated tuner approach for load‐pull measurement of Si/SiGe:C HBT at 200 GHz

Load impedance variations were obtained using an innovative integrated tuner at G-band. The 200 GHz load-pull measurements on a silicon–germanium (SiGe) heterojunction bipolar transistor (HBT) are presented. First, the linearity of the integrated tuner is checked. Then, the main load-pull characteristics are extracted from a 0.13 × 3 µm2 emitter area SiGe HBT. The aim of this study is to provide a solution to avoid losses related to probes and commercial tuners. Thereby, from design to measurements, power setup architecture, calibration and performances at 200 GHz are performed in a non-50 Ω environment. Finally, comparisons between measurements and simulation from a high current model (HICUM) show good agreement, demonstrating the capability of the measurement approach.

Influence of base resistance on extracting thermal resistance for SiGe HBTs

In this article, the influence of base resistance on extracting thermal resistance for SiGe heterojunction bipolar transistors is studied and an improved approach for determining the junction temperature and thermal resistance is presented. The proposed method for extracting thermal resistance is based on the temperature sensitivity of the base–emitter (B–E) voltage when the device is biased with a fixed emitter current density. This approach not only takes into account the self-heating during the different ambient temperature measurement but also revises the empirical equation of B–E voltage due to the influence of base resistance during the power dissipation increment measurement. Results are obtained for devices with different emitter lengths and fingers. Compared with the conventional method, the thermal resistance is about up to 15% improvement for the device with 0.3 × 1.9 μm2 emitter area and 13.8% for the device with 0.3 × 13.9 μm2 emitter area. The accurate thermal resistance implemented in HICUM model has resulted in better fit for transistor output characteristics. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Fabrication and Characterization of Self-Aligned InAlAs/InGaAsSb/InGaAs Double Heterojunction Bipolar Transistors

A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52Al0.48As/In0.42Ga0.58As0.77Sb0.23/ In0.53Ga0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65 x 8.65 µm2 emitter area were obtained. A unity gain cut-off frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC = 302 kA/cm2 were achieved.

An improved small-signal model for SiGe HBTs

Accurate equivalent-circuit modelling is a prerequisite for the circuit design. In this article, an improved small-signal equivalent-circuit model for silicon–germanium heterojunction bipolar transistors (SiGe HBTs) is proposed. The proposed model has taken into account the effects of the base and collector metallisations, and the corresponding extraction method of the substrate elements is developed. The extraction approach is validated with SiGe HBTs fabricated with a 0.35-µm BiCMOS technology, µm2 emitter area from 50 MHz to 10 GHz. The agreements between the measured and modelled data are excellent in the desired frequency range over a wide range of bias points with different bias conditions.

Fabrication of InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors

A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52Al0.48As/In0.42Ga0.58As0.77Sb0.23/In0.53Ga0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65×8.65 μm2 emitter area were obtained. A unity gain cutoff frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC=302 kA/cm2 were achieved.

MEXTRAM model based SiGe HBT large-signal modeling

An improved large-signal equivalent-circuit model for SiGe HBTs based on the MEXTRAM model (level 504.5) is proposed. The proposed model takes into account the soft knee effect. The model keeps the main features of the MEXTRAM model even though some simplifications have been made in the equivalent circuit topology. This model is validated in DC and AC analyses for SiGe HBTs fabricated with 0.35-μm BiCMOS technology, 1 × 8 μm2 emitter area. Good agreement is achieved between the measured and modeled results for DC and S-parameters (from 50 MHz to 20 GHz), which shows that the proposed model is accurate and reliable. The model has been implemented in Verilog-A using the ADS circuit simulator.

Possibility of Terahertz Amplification by Active Transmission Lines Loaded with Resonant Tunneling Diode Pairs

Active transmission lines loaded with resonant tunneling diode (RTD) pairs were investigated as possible THz amplifiers. The RTD pair consists of two RTDs connected serially and is biased by voltages of the same absolute value with opposite signs. The RTD pair has unique current–voltage characteristics at the intermediate node; the true negative resistance appears in the low-voltage region. The linearity of this region is good owing to the symmetry of the circuit. Moreover, the RTD pair circuit can be stabilized more easily than that of a single RTD. On the basis of these advantages, the RTD pair transmission lines are a promising candidate for THz amplifiers. RF signal amplification was demonstrated by circuit simulation. The cutoff frequency was also demonstrated to increase with decreasing unit cell size, and it exceeds 1 THz with RTDs of 1 µm2 emitter area.

Improved analytical method for determination of small-signal equivalent-circuit model parameters for InP∕InGaAs HBTs

An improved direct extraction method for determination of the small-signal equivalent-circuit model for InP/InGaAs double heterojunction bipolar transistors is presented. This method is based on an accurate small-signal model, which takes into account the base-emitter and collector-emitter metalisations by using two additional capacitances Cmb and Cmc. These capacitances (Cmb and Cmc) are extracted using a set of exact closed-form equations. Significant improvement of the extraction accuracy of the intrinsic base-emitter junction capacitance Cbe is obtained by using the new combination method, which is based on the relationship between the conventional T- and PI-type equivalent-circuit topology. The approach has been verified over a wide range of bias points using an InP HBT with 5×5 μm2 emitter area in the frequency range of 50 MHz–40 GHz.

Type-II GaAsSb/InP heterojunction bipolar light-emitting transistor

We report radiative recombination in the base layer of Type-II InP/GaAsSb/InP double heterojunction bipolar light-emitting transistors (HBLET) operating in the common-emitter configuration. The typical current gain, β, for a 120×120 μm2 emitter area of the HBLET is 38. The optical emission wavelength from a 30 nm GaAs0.51Sb0.49 base is centered at λpeak=1600 nm. Three-port operation of the Type-II HBLET with simultaneously an amplified electrical output and an optical output with signal modulation is demonstrated at 10 kHz.

Metamorphic InP/InGaAs double-heterojunction bipolar transistors on GaAs grown by molecular-beam epitaxy

InP/InGaAs double-heterojunction bipolar transistor (HBT) structures were grown metamorphically on GaAs substrates by solid-source molecular-beam epitaxy. A linearly graded InxGa1−xP (x varying from 0.48 to 1) buffer layer was used to accommodate the strain relaxation. The crystallinity of the buffer layer and the HBT structure was examined by x-ray diffractometry. Devices with 5×5 μm2 emitter area showed a typical peak current gain of 40, a common-emitter breakdown voltage (BVCEO) higher than 9 V, a current gain cut-off frequency (fT) of 46 GHz, and a maximum oscillation frequency (fmax) of 40 GHz.

High performance InGaP/GaAs HBTs for mobile communications

High performance InGaP/GaAs heterojunction bipolar transistors (HBTs) with a maximum DC current gain of &gt; 100 and fmax &gt; 120 GHz (3 × 30 µm2 emitter area) have been developed using production-like processes (4 inch wafers, i-line stepper lithography). The fabricated L-band low voltage (≥ 2 V) power cell HBTs with 12 × 3 × 30 µm2 emitter area have a 1 W output power with &gt; 63% power added efficiency at 3 V operating bias and 2 GHz.

Fabrication and Characterization of InP Heterojunction Bipolar Transistors with Emitter Edges Parallel to [001] and [010] Crystal Orientations

We present a study of fully-self aligned InP-based heterojunction bipolar transistors (HBTs) with the emitter edges oriented parallel to the [0,0,1] and [0,1,0] crystal orientations. A technology based on vertical and lateral wet etching of InP was developed to fabricate emitter-up and collector-up InP/InGaAs HBTs with reduced parasitic resistances and capacitances. For emitter-up HBTs, the undercut distance between the base contact and the emitter active area was <0.3 µm in all directions, and high frequency performance of fT=105 GHz and fMAX=82 GHz were obtained for a 4×12 µm2 emitter area. For collector-up metal HBTs (MHBTs), emitter widths as small as 0.5 µm were formed by lateral wet etching with a relative area fluctuation less than 10%, and high frequency performance of fT=40 GHz and fMAX=160 GHz were obtained for a 0.5×52 µm2 emitter area.

High-speed carbon-doped-base InP/InGaAs heterojunction bipolar transistors grown by MOCVD

State of the art fT and fmax values of 135 and 113 GHz for MOCVD grown C-doped base InP/InGaAs HBTs are achieved with a 0.5 × 4.7 µm2 emitter area device. A rapid increase in fT at a very low VCE value of 0.3 V owing to the abrupt base dopant profile demonstrates the suitability of C-doped-base HBTs for high-speed and low-power circuit applications.

Microwave operation of high power InGaP/GaAs heterojunction bipolar transistors

The first high power demonstration of an InGaP/GaAs heterojunction bipolar transistor is presented. Multifinger selfaligned HBTs were tested at 3 GHz. A maximum output power of 2.82 W CW was obtained for a 600 μm2 emitter area device (4.7 mW/μm2 power density) with an attendant gain of 6.92 dB; simultaneously, the device exhibited 55.2% power added efficiency, 69.1% collector efficiency and 8.0 × 104 A/cm2 emitter current density.

InGaAs/InP double-heterojunction bipolar transistors with step graded InGaAsP between InGaAs base and InP collector grown by metalorganic chemical vapor deposition

We have fabricated InGaAs/InP double-heterojunction bipolar transistors (DHBTs) grown by metalorganic chemical vapor deposition (MOCVD). By inserting step graded InGaAsP layers between p+-InGaAs base and n−-InP collector, the current gain of DHBTs with the graded layers was about twice as large as that without the graded layers, and the dependence of collector current on collector/emitter voltage was smaller than that without graded layers. The current gain was measured up to 2300 with 25×25 μm2 emitter area at a collector current density of 1×104 A/cm2.

In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistor on GaAs by molecular beam epitaxy

We report on the first In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors grown on a GaAs substrate. In order to suppress the propagation of threading dislocations to the surface, a ten-period AlAs/In0.52Al0.48As (20 Å/20 Å) strained-layer superlattice was repeated twice with intervening undoped In0.52Al0.48As layers. The typical common emitter current gain in 50×50 μm2 emitter area devices was 50, with a maximum of 63, at a collector current density of 2×103 A/cm2.