Power Heterojunction Bipolar Transistors Research Articles

Design and Optimization of a Highly Linear Power Amplifier with Novel Active Bias Circuit in InGaP/GaAs HBT MMIC Technology

This paper introduces a highly linear power amplifier (PA) that utilizes a 2-μm InGaP/GaAs hetero-junction bipolar transistor (HBT) process. As communication systems evolve in complexity, the demands for the linearity and static power consumption of HBT power amplifiers are becoming more stringent. Typically, there exists a trade-off relationship between linearity and static power consumption in the design process. Hence, this paper proposes a novel active bias circuit for HBT power amplifiers, along with its layout design. The proposed active bias circuit consists of a differential pair and a current mirror structure, designed to enhance PA linearity while maintaining low quiescent current. Additionally, a novel layout structure is implemented to achieve thermal coupling between the RF transistors and the active bias, further improving PA linearity. As a result of the implementation of the proposed active bias and layout structure, the PA demonstrates high linearity in both amplitude modulation to phase modulation (AM/PM) and amplitude modulation to amplitude modulation (AM/AM) performance, while simultaneously maintaining a low quiescent current. The three-stage PA prototype achieves notable performance metrics, including a peak gain of 32.6 dB at 5.6 GHz, gain flatness of ±0.5 dB from 5.15 GHz to 5.85 GHz, and P1dB of 32.1 dBm at a quiescent emitter current of 180 mA.

Simulation and Comprehensive Analysis of AlGaN/GaN HBT for High Voltage and High Current

We present a series of TCAD analysis of gallium nitride (GaN) heterojunction bipolar transistors (HBTs) that investigates the impact of various key parameters on the gain characteristics, output characteristics, and breakdown characteristics. It has been observed that the DC gain of the AlGaN/GaN HBTs exhibits a non-linear relationship with the increase in the Al fraction. Specifically, the DC gain initially rises, then declines after reaching its peak value at approximately 7%. By optimizing the concentration of the base and the concentration and thickness of the collector epitaxial layer, it is possible to achieve devices with breakdown voltages of 1270 V (with a collector thickness of 6 μm and a carrier concentration of 2 × 1016 cm−3), specific on-resistance of 0.88 mΩ·cm2, and a current gain of 73. In addition, an investigation on breakdown characteristics is conducted for HBTs with two types of substrates, namely QV-HBTs and FV-HBTs, at different inclinations of the ramp. We propose that critical angles are 79° and 69° to prevent the surface breakdown of the device, which helps to achieve an avalanche in GaN HBTs. We anticipate that the aforementioned findings will offer valuable insights for designing GaN-based power HBTs with elevated breakdown thresholds, heightened current densities, and increased power capabilities.

Multi-Band Power Amplifier Module with Back-Off Efficiency Improvement using Ultra-Compact 3D Vertical Stack Multi-Chip Package for Cellular Handsets.

A highly integrated multi-mode multi-band (MMMB) power amplifier module (PAM) using hybrid bulk complementary metal oxide semiconductor (CMOS), gallium arsenide (GaAs) heterojunction bipolar transistor (HBT), and silicon-on-insulator (SOI) technologies for low band (LB, 824-915 MHz) and high band (HB, 1710-1980 MHz) is proposed. The hybrid MMMB PAM integrates a bulk CMOS controller die, a GaAs HBT power amplifier (PA) die and a SOI switch die on a six-layer laminate. To simultaneously obtain both highly efficient and highly linear characteristics over a wide range of input power levels, a parallel dual-chain PA strategy has been adopted to provide vary bias current and gain for low-power mode (LPM) and high-power mode (HPM) operation. Additionally, a broadband two-section low-pass output matching network design based on the suppression of high-order harmonics is proposed for enhanced efficiency and linearity. In order to achieve further miniaturization, a three-dimensional (3D) die stack multi-chip module (MCM) packaging structure, where the presented CMOS controller die is stacked vertically on the GaAs HBT PA die, is implemented. The measurement results show that the fabricated MMMB PAM achieves 26.1-27 dB of power gains and 38-38.4% of PAEs at an output power (Pout) of 28 dBm in the HPM, and 20.4-20.9 dB of power gains and 12.4-13.8% of PAEs at Pout of 17 dBm in the LPM over LB. For HB, power gains of 24.3-26.7 dB while maintaining PAEs of 38.2-39.9% at Pout of 28 dBm, and power gains of 15.9-17.5 dB while maintaining PAEs of 12.3-12.8% at Pout of 17 dBm are realized in the HPM and LPM, respectively. The fabricated PAM covering five frequency bands and operating at two power modes only occupies a 5 × 3.5 mm2 area. To the best of the authors' knowledge, this work is the first demonstration of a MMMB PAM adopting an ultra-compact 3D vertical stack MCM package with favorable RF performance.

A fully integrated GaAs HBT power amplifier with enhanced efficiency for 5-GHz WLAN applications

An efficiency-enhanced fully integrated power amplifier (PA) for wireless local area networks (WLANs) was implemented based on the GaAs heterojunction bipolar transistor (HBT) process. A harmonic tuning network that can absorb the parasitic inductance of the bonding wires is proposed, which reduces the chip area significantly. The network provides nearly optimum fundamental and second harmonic impedances from 5.0 to 5.5 GHz. Additionally, a novel adaptive bias circuit that corrects the AM-AM and AM-PM distortion and improve thermal stability at high input power was proposed. With a chip dimension of only 1.06 mm2, the PA achieves a gain of 31.1-31.6 dB and saturated power of 29.9-30.3 dBm with a peak power-added efficiency (PAE) of 49.3%-51.8% across 5.0-5.5 GHz. The PA also shows an output power of 22.1 dBm (EVM=-32 dB) with 18.4% PAE under an 802.11ac MCS9 VHT160 test signal. In addition, the PA delivers 17.5 dBm (EVM=-42 dB) output power when tested with the 802.11ax MCS11 VHT160 signal at 5.25 GHz.

Highly Linear High-Power 802.11ac/ax WLAN SiGe HBT Power Amplifiers With a Compact 2nd-Harmonic-Shorted Four-Way Transformer and a Thermally Compensating Dynamic Bias Circuit

This article presents the design of a highly linear high-power silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) 802.11ac/aχ wireless local area network (WLAN) power amplifiers (PAs). The challenges associated with electrothermal effects on the dynamic operation of WLAN PAs are first discussed. We then propose the design methods that take into account the electrothermal transient effect to improve linear output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">οUT</sub> ) and dynamic error vector magnitude (DEVM). A compact four-way output transformer balun is proposed to achieve efficient power combining, and a built-in 2nd-harmonic short is demonstrated by using a novel multi-layered metallization scheme. A thermally compensating dynamic bias circuit that improves the DEVM and reduces memory effects is designed with an integrated temperature sensor. Different SiGe HBT array layouts, laterally and vertically arranged, of the output stage of the PA are also investigated. With the 802.11ac MCS9 VHT80 test signals, the DEVM of a PA with a laterally arranged output stage is lower than that of its vertical counterpart. This suggests the importance of the layout on the transistor electrothermal transient effect. The PA with the laterally arranged output stage shows a P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">οUT</sub> of 22.5/23.6/23.2 dBm (DEVM = -35 dB) with 10.0/12.2/11.2% power-added efficiency (PAE) at 5210/5530/5855 MHz under an 802.11ac MCS9 VHT80 test signal at 50% duty cycle. Good DEVM performance was measured under the test signal with various duty cycles, indicating that the proposed PA is thermally robust. The design supports the 802.11ax MCS11 VHT80 signals with 19.4-dBm P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">οUT</sub> , satisfying a DEVM of -40 dB.

A 4.2-to-5.4 GHz stacked GaAs HBT power amplifier for C-band applications

PurposePower amplifiers (PAs) play an important role in wireless communications because they dominate system performance. High-linearity broadband PAs are of great value for potential use in multi-band system implementation. The purpose of this paper is to present a cascode power amplifier architecture to achieve high power and high efficiency requirements for 4.2∼5.4 GHz applications.Design/methodology/approachA common emitter (CE) configuration with a stacked common base configuration of heterojunction bipolar transistor (HBT) is used to achieve high power. T-type matching network is used as input matching network. To increase the bandwidth, the output matching networks are implemented using the two L-networks.FindingsBy using the proposed method, the stacked PA demonstrates a maximum saturated output power of 26.2 dBm, a compact chip size of 1.17 × 0.59 mm2 and a maximum power-added efficiency of 46.3 per cent. The PA shows a wideband small signal gain with less than 3 dB variation over working frequency. The saturated output power of the proposed PA is higher than 25 dBm between 4.2 and 5.4 GHz.Originality/valueThe technology adopted for the design of the 4.2-to-5.4 GHz stacked PA is the 2-µm gallium arsenide HBT process. Based on the proposed method, a better power performance of 3 dB improvement can be achieved as compared with the conventional CE or common-source amplifier because of high output stacking impedance.

A broadband 23.1 ∼ 27.2 GHz doherty power amplifier with peak output power of 24.3 dBm

Purpose This paper aims to implement a new high output power fully integrated 23.1 to 27.2 GHz gallium arsenide heterojunction bipolar transistor power amplifier (PA) to meet the stringent linearity requirements of LTE systems. Design/methodology/approach The direct input power dividing technique is used on the chip. Broadband input and output matching techniques are used for broadband Doherty operation. Findings The PA achieves a small-signal gain of 22.8 dB at 25.1 GHz and a saturated output power of 24.3 dBm at 25.1 GHz with a maximum power added efficiency of 31.7%. The PA occupies 1.56 mm2 (including pads) and consumes a maximum current of 79.91 mA from a 9 V supply. Originality/value In this paper, the author proposed a novel direct input dividing technique with broadband matching circuits using a low Q output matching technique, and demonstrated a fully-integrated Doherty PA across frequencies of 23.1∼27.2 GHz for long term evolution-license auxiliary access (LTE-LAA) handset applications.

Thermal resistance matrix representation of thermal effects and thermal design of microwave power HBTs with two-dimensional array layout**Project supported by the National Natural Science Foundation of China (Grant Nos. 61006059 and 61774012), Beijing Municipal Natural Science Foundation, China (Grant No. 4143059), Beijing Municipal Education Committee, China (Grant No. KM201710005027), Postdoctoral Science Foundation of Beijing, China (Grant No. 2015ZZ-11), China Postdoctoral

Based on the thermal network of the two-dimensional heterojunction bipolar transistors (HBTs) array, the thermal resistance matrix is presented, including the self-heating thermal resistance and thermal coupling resistance to describe the self-heating and thermal coupling effects, respectively. For HBT cells along the emitter length direction, the thermal coupling resistance is far smaller than the self-heating thermal resistance, and the peak junction temperature is mainly determined by the self-heating thermal resistance. However, the thermal coupling resistance is in the same order with the self-heating thermal resistance for HBT cells along the emitter width direction. Furthermore, the dependence of the thermal resistance matrix on cell spacing along the emitter length direction and cell spacing along the emitter width direction is also investigated, respectively. It is shown that the moderate increase of cell spacings along the emitter length direction and the emitter width direction could effectively lower the self-heating thermal resistance and thermal coupling resistance, and hence the peak junction temperature is decreased, which sheds light on adopting a two-dimensional non-uniform cell spacing layout to improve the uneven temperature distribution. By taking a 2 × 6 HBTs array for example, a two-dimensional non-uniform cell spacing layout is designed, which can effectively lower the peak junction temperature and reduce the non-uniformity of the dissipated power. For the HBTs array with optimized layout, the high power-handling capability and thermal dissipation capability are kept when the bias voltage increases.

Impact of finger numbers on the performance of proton-radiated SiGe power HBTs at room and cryogenic temperatures

Multi-finger silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) are attractive to the radiation-intense environment. This paper investigates the performance of proton-radiated SiGe power HBTs with different finger numbers (8, 24, 40, and 80 emitter fingers) at room and cryogenic temperatures. Different proton radiation fluences (1 × 1012 p/cm2, 2 × 1013 p/cm2, and 5 × 1013 p/cm2) and ambient temperatures (300 K and 77 K) were used to study the irradiation performance of the HBTs. Results show that the number of emitter fingers has a significant impact on the performance of the SiGe power HBTs for different temperatures and irradiation conditions. Underlying mechanisms have been discussed. This study provides guidelines on designing and using SiGe power HBTs for integrated circuits in radiation environments at room and cryogenic temperatures.

A 5.7–6.4GHz GaAs HBT Power Amplifier with a Gain Enhanced Bias Circuit

This paper describes the design of a 5.7- 6.4GHz GaAs Heterojunction bipolar transistor (HBT) power amplifier for broadband wireless application such as wireless metropolitan area networks. A bias circuit is proposed which enhances the power gain and provides a good linearity. Using the wideband matching network techniques with trap circuits embedded to filter the harmonics and the diode-based linearizing techniques, a broadband power amplifier module was obtained which exhibited a gain above 28dB. This is about 1dB improvement compared with those normal bias circuits at a supply voltage of 5V in the frequency range of 5.7-6.4GHz, measured with Continuous wave(CW) signals. The saturated output power was greater than 33dBm in 5.7-6.4GHz and the output 1dB compression point was greater than 31dBm. The phase deviation was less than 5 degrees when the output power below 33dBm. The second and third order harmonic components were also less than -45dBc and -50dBc.

Electrothermal Effects on Performance of GaAs HBT Power Amplifier During Power Versus Time (PVT) Variation at GSM/DCS Bands

Power versus time (PVT) variation is one of the most important features for describing electrothermal performance of RF power amplifiers (PAs) for global system for mobile communication/digital cellular system bands. The PA sometimes produces high power at the first time slot and low power at the second time slot, which results in similar temperature variation caused by its self-heating effect. Therefore, both theoretical and experimental investigations are carried out for capturing electrothermal effects on the performance of GaAs-based heterojunction bipolar transistor (HBT) PAs. The temperature distribution over the PA die is obtained using our in-house developed finite-element method algorithm and a thermal infrared scanner, respectively. In particular, the PVT variation of the PA for a two time slot, as well as a four time slot (i.e., 75% of its operation time is in the “power on” state) case is studied in detail. Furthermore, an improved design for the GaAs HBT PA chip is performed, fabricated, and tested with its PVT variation suppressed effectively. This study should be very useful for the development of PAs for many wireless communications.

Transistor Model Building for a Microwave Power Heterojunction Bipolar Transistor

This article describes the detailed development of a large-signal transistor model for a microwave power heterojunction bipolar transistor (HBT). Based on the neurospace-mapping (Neuro-SM) technique, this model uses neural networks to map a coarse model space represented by the existing model simulations onto the fine model space represented by device measurements. This article tied for first place in the Microwave Transistor Modeling Student Design Competition at the 2014 IEEE International Microwave Symposium (IMS2014) held in Tampa, Florida.

Failure Model Research of Power HBTs

Heterojunction bipolar transistors (HBTs) are playing an important role in microwave and power applications. When HBTs operated at high power, the power dissipation and self-heating effects will enable the generation of electrical properties in the transistor failure. The failure experiment system of microwave power HBTs was established. Based on this system, the changes of electrical parameters of HBTs in deferent stress, such as Gummel plots, base current various different base-emitter voltage and base-collector voltage, were measured and analyzed. At the same time, the failure of base current of SiGe HBTs under the condition of FC, SC and thermal stress are studied respectively. It was found that ΔIBis the sensitive parameter of electrical and thermal stress. Based on this reason, we presented the failure model of IB. This model could explain the experiment phenomenon successfully, which is very important and useful for applications of microwave power analog IC’s.

EXPERIMENTAL CHARACTERIZATION OF PROTON RADIATED SiGe POWER HBTs AT EXTREME TEMPERATURES

The performances of proton irradiated silicon–germanium (SiGe) power heterojunction bipolar transistors (HBTs) at extreme temperatures (liquid nitrogen temperature and high stage-temperature of 120°C with junction temperature over 160°C) are reported in this work. SiGe power HBTs with total emitter area of ~ 1460 μm2 are fabricated in a commercial BiCMOS process, and irradiated with proton at different fluences from 1 × 1012 p/cm2 to 5 × 1013 p/cm2. Experimental characterizations are conducted for pre- and post-radiation devices at room temperature, cryogenic temperature and high temperature. The results demonstrate that the proton-irradiated SiGe power HBTs are naturally suitable for electronic operations at extreme temperatures. Specifically, investigation of proton radiation on SiGe power HBTs at liquid nitrogen temperature (77 K) indicates a significant potential for space applications. In addition, SiGe power HBTs show better tolerance of proton radiation at high temperature of 120°C (junction temperature over 160°C). SiGe power HBTs demonstrate great potential in power amplification for wireless communication systems under severe radiation and extreme temperature environment (cryogenic and high temperatures) even without any intentional radiation hardening.

Analytical Design Method for a Low-Distortion Microwave InGaP/GaAs HBT Amplifier Based on Transient Thermal Behavior in a GaAs Substrate

Based on the transient thermal behavior in a GaAs substrate, the distortion caused by the self-heating effect in an InGaP/GaAs heterojunction bipolar transistor (HBT) has been analytically compensated. The temperature-time variation in a transistor depends on the thermal characteristics of a semiconductor substrate at the base-band range. For a wideband digital modulated signal as input, a multistage thermal resistor-thermal capacitor ladder circuit is used as a model to emulate the thermal characteristics. The distortion analysis is based on Taylor and Volterra series expansion techniques including both electrical and thermal effects. In addition, a compensation condition for the distortion caused by the thermal influence is also successfully derived based on distortion analysis. The validity of the proposed analytical method is shown for an InGaP/GaAs HBT power amplifier operating at 1.95 GHz. The analytical design results are in good agreement with the measured results.

A high-linearity InGaP/GaAs HBT power amplifier for IEEE 802.11a/n

A three-stage 4.8–6 GHz monolithic power amplifier (PA) compatible with IEEE 802.11a/n designed based on an advanced 2 μm InGaP/GaAs hetero-junction bipolar transistor (HBT) process is presented. The PA integrates input matching and closed-loop power control circuits on chip. Under 3.3 V DC bias, the amplifier achieves a ∼31 dB small signal gain, excellent wide band input and output matching among overall 1.2 GHz bandwidth, and up to 24.5 dBm linear output power below EVM 3% with IEEE 802.11a 64QAM OFDM input signal.

1-Watt highly linear HBT power amplifier driver integrated circuit with low current consumption

This article presents a power amplifiers (PA) driver IC which has a parallel combined structure with a dual bias network.Each PA cell for parallel combination has an optimized bias to achieve both lower current consumption and IM3 cancellation at the same time, so that the overall PA driver IC has an improved linearity with a low current consumption. An incomplete Wilkinson divider including an input matching capability was proposed. This was adopted to prevent a stability degradation which can be caused by a parallel combination. The proposed PA driver IC was designed. This was implemented using a 2-μm InGaP/GaAs heterojunction bipolar transistor (HBT) to have an output power of 1 Watt. The quiescent currents for the upper and lower PA cells were optimized to have the best compromised performances with quiescent current levels of 100 and 150 mA, respectively. By the implemented PA driver IC, a gain of 17.25 dB and a high power-added efficiency of 54.15% at a P1dB of 31 dBm were achieved at a center frequency of 900 MHz. For a two-tone signal having a tone-spacing of 1 MHz, it also exhibited a high output IP3 of 54.28 dBm at an output power level of 20 dBm. The average output power was 22.36 dBm to which the IMD3 level should be lower than −60 dBc. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1680–1683, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27639

Novel Multi-Finger Power HBTs with Non-Uniform Segmented Emitter for Thermal Stability Enhancement

With the aid of a two-dimensional thermal-electrical model, the thermal stability of multi-finger power heterojunction bipolar transistors (HBTs) with uniform segmented emitter, and non-uniform segmented emitter are studied. It shows that both of them could lower the peak temperature and improve the non-uniformity of the collector current density distribution, and thus improve the thermal stability, compared with an HBT which has traditional non-segmented emitter structure. At the same time, the improvement capability of thermal stability for HBT with non-uniform segmented emitter is superior to that of HBT with uniform segmented emitter, ascribing to selectively divide the emitter fingers into various segments according to the difference of heat dissipation capability in emitter fingers. Furthermore, the improvement capability of thermal stability for HBT with non-uniform segmented emitter is enhanced exponentially as segment spacing increases. However, for HBT with uniform segmented emitter, the ability is less sensitive to the increasing of the segment spacing as it exceeds 6μm. Therefore, the technique of non-uniform segmented emitter is a better method for enhancing the thermal stability of power HBTs.

RF characteristics of proton radiated large-area SiGe HBTs at extreme temperatures

The radio frequency (RF) characteristics of proton irradiated large-area silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) at extreme temperatures (liquid nitrogen temperature of 77K and high temperature of ∼430K) are reported in this work. Large emitter area high-power SiGe HBTs fabricated in a commercial BiCMOS process were irradiated with proton, at various fluences from 1×1012p/cm2 to 5×1013p/cm2. Small-signal ac experimental characterizations were achieved for pre- and post-radiation devices at room temperature, cryogenic and high temperatures. We show that proton radiated large-area SiGe HBTs are naturally suitable for electronic operations at extreme temperatures. Investigation of proton radiation on large-area SiGe HBTs at liquid nitrogen temperature (77K) demonstrates great potential of SiGe power HBTs for space applications. Moreover, performance of proton radiated SiGe power HBTs at high temperature of ∼430K indicates a better tolerance of proton radiation than room temperature. Possible underlying mechanisms for the improvement of radiation robustness at cryogenic and high temperatures are discussed. The results demonstrate the possibility of using large-area SiGe HBTs in power amplification for wireless applications under severe radiation and extreme temperature environment without any intentional radiation hardening.

High-Directivity Enhancement With Passive and Active Bypass Circuit Techniques for GaAs MMIC Microstrip Directional Couplers

This paper describes monolithic microwave integrated circuit microstrip directional couplers based on a new directivity enhancement technique. This technique utilizes a bypass circuit-a phase shifter and an attenuator-placed between the coupling and isolation ports to cancel out backward wave leakage to the coupling port, thereby enhancing directivity of the couplers. The bypass circuit can be implemented with a simple passive LCR circuit or an active heterojunction bipolar transistor (HBT) phase-inversion attenuation circuit. Edge-coupled-type microstrip spiral couplers using the passive and active bypass circuits were fabricated in a GaAs HBT process. Measurements are as follows. The coupler with the passive LCR bypass circuit delivers a -21-dB coupling factor and a 0.14-dB insertion loss (IL) at 2.6 GHz while keeping enhanced directivity of more than 30 dB with a 23.1% relative bandwidth. This corresponds to more than 21-dB improvement of directivity at the same frequency, compared to the coupler without the bypass circuit. For the coupler with the active attenuator, a peak directivity of 46 dB and more than 30-dB directivity with a 120% relative bandwidth are achieved while a -21-dB coupling factor and a 0.13-dB IL are delivered at 2 GHz. Additional measurements of HBT power detectors integrated with the couplers show that the couplers with passive and active bypass circuits can suppress detection errors of less than ±0.20 and ±0.10 dB, respectively, under 4:1 voltage standing-wave ratio load mismatching conditions, thus proving the effectiveness of the bypass techniques.