Integration of GaInP/GaAs heterojunction bipolar transistors and high electron mobility transistors

Integration of carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBT's) and high electron mobility transistors (HEMT's) is demonstrated by growing an HBT on the top of a HEMT. A current gain of 60. a cutoff frequency of 59 GHz and a maximum oscillation frequency of 68 GHz were obtained for a 5 × 15 μm 2 self-aligned HBT. The HEMT with a gate length of 1.5 μm has a transconductance of 210 mS/mm, a cutoff frequency of 9 GHz and a maximum oscillation frequency of 22 GHz. It is shown that the GaInP/GaAs HBT on the HEMT is the simple Bi-FET tecnology suitable for microwave and mixed single applications.published_or_final_versio

Novel InGaP/GaAsSb/GaAs DHBTs

A study of the InGaP/GaAsSb/GaAs double heterojunction bipolar transistor (DHBT) is presented. Novel device structure is designed. A fully strained pseudomorphic GaAsSb with 8.0% Sb composition is used as the base layer, while an InGaP layer as the emitter which both eliminates the misfit dislocations and increases the valence band discontinuity at the InGaP/GaAsSb interface. A current gain of 22.6 has been obtained from the InGaP/GaAsSb/GaAs DHBT. Typical turn-on voltage of the device is 0.973 V which is 0.116V lower than that of traditional InGaP/GaAs HBT. Moreover, the current transport mechanism of the InGaP/GaAsSb/GaAs DHBTs is investigated. These results show that GaAsSb is a promising base material for reducing the turn-on voltage of GaAs HBTs.published_or_final_versio

CCl4-doped semi-insulating InP as a buffer layer in GaInAs/InP high electron mobility transistors

The application of CCl4-doped semi-insulating InP as a buffer layer in a pseudomorphic Ga0.2In0.8P/Ga0.47In0.53As/InP high electron mobility transistor (HEMT) grown by metalorganic chemical vapor deposition is reported. This Al-free InP-base HEMT with a gate length of 1.3 μm has extrinsic transconductances of 420 and 610 mS/mm at 300 and 77 K, respectively. A cutoff frequency of 15 GHz and a maximum oscillation frequency of 40 GHz are obtained. The results demonstrate the CCl4-doped semi-insulating InP is a promising buffer layer for InP-based HEMT. © 1996 American Institute of Physics.published_or_final_versio

A high-frequency GaInP/GaAs heterojunction bipolar transistor with reduced base-collector capacitance using a selective buried sub-collector

A C-doped GaInP/GaAs HBT using a selective buried sub-cellular has been fabricated by two growth steps. The device was fabricated with minimum overlap of the extrinsic base reduced to about half of that of an HBT without selective buried sub-collector while the base resistance remains unchanged. A current gain of 35, f T of 50 GHz and f max of 140 GHz are obtained with this technology.published_or_final_versio

Identifying Leadership Competencies for Construction 4.0

With the development of the times, the challenge of the construction industry entering Construction 4.0 and surviving in it is still formidable. Although many studies state the importance of effective leadership in the context of Construction 4.0, there is a need to investigate what leadership qualities can eectively provide guidance on leading construction organisations in this era. Through a focused review, this study aims to propose a series of key leadership competencies in the context of Construction 4.0 for guiding the digital transformation and the development of leaders in construction organisations, as well as complementing the existing Construction 4.0 research gap in organisational management. Through in-depth analysis of the retrieved literature, this research extracted and analysed 22 leadership competencies, classified them into four top-level themes (cognition, interpersonal communication, business, and strategy), and discussed the potential relationships among them. Theoretically, the article provides the basis and guidance for future leadership research by redefining and explaining the meaning of each competency. In practice, the paper provides construction industry practitioners with guidance on the development of effective leadership in the era of Construction 4.0

Temperature dependence of current gain of GalnP/GaAs heteroj unction and heterostructure-emitter bipolar transistors

The temperature effect on current gain is presented for GalnP/GaAs heterojunction and heterostructure-emitter bipolar transistors (HBT's and HEBT's). Experimental results showed that the current gain of the HEBT increases with the increase of temperature in the temperature range of 25-125 °C and decreases slightly at temperatures above 150 °C. The smaller the collector current, the larger is the positive differential temperature coefficient. At high current levels, the current gain dependence on temperature is significantly reduced. On the other hand, a large negative coefficient is observed in the HBT in all current range. This finding indicates that the HEBT is a better candidate than the HBT for power devices. © 1999 IEEE Publisher Item Identifier S 0018-9383(99)00257-9.published_or_final_versio

Carbon-doped GaInP/GaAs heterojunction bipolar transistors grown by metalorganic chemical vapor deposition using nitrogen as the carrier gas

The use of nitrogen as the carrier gas in metalorganic chemical vapor deposition (MOCVD) for the growth of carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) is reported. The material quality grown using a nitrogen carrier gas is the same as that of using a hydrogen carrier gas. High carbon doping and hole concentrations of 3 × 1020 and 2 × 1020 cm-3 in GaAs were obtained. The fabricated HBTs showed very good DC and RF performances indicating that nitrogen can be a promising carrier gas for MOCVD growth. © 1997 American Institute of Physics.published_or_final_versio

High efficiency, low offset voltage InGaP/GaAs power heterostructure-emitter bipolar transistors with advanced thermal management

High efficiency, low offset voltage InGaP/GaAs power heterostructure-emitter bipolar transistors (HEBTs) have been demonstrated. The large signal performance of the HEBTs is characterized. Output power of 0.25 W with power added efficiency (PAE) of 63.5% at 1.9 GHz has been achieved from a 26-finger HEBT with total emitter area of 873.6 μm2. Output power of 1.0 W with PAE of 63% has been obtained from the composition of four above-mentioned power cells at the optimum conditions of impedance matching. The thermal performance of HEBT is presented and the results show better thermal management than conventional HBT. The experimental results demonstrate good power performance and capability of HEBTs.published_or_final_versio

Fabrication and characteristics of a GaInP/GaAs heterojunction bipolar transistor using a selective buried sub-collector

A C-doped GaInP/GaAs heterojunction bipolar transistor (HBT) with a selective buried sub-collector has been fabricated by two growth steps. The active HBT region was made on the selective buried sub-collector layer with minimum overlap of the extrinsic base and the sub-collector region resulting in substantial reduction of the base-collector capacitance. The experiment shows that the base-collector capacitance is reduced to about half of that of a conventional HBT while the base resistance remains unchanged resulting in a 40-50% increase in the maximum oscillation frequency. Both DC and RF characteristics are investigated and compared with a conventional HBT. A current gain of 40 cutoff frequency of 50 GHz and maximum oscillation frequency of 140 GHz were obtained for the GaInP/GaAs HBT. It is demonstrated that the selective buried sub-collector provides an effective means for enhancing RF performance of an HBT. © 1997 IEEE.published_or_final_versio

A class of nonzero-sum investment and reinsurance games subject to systematic risks

© 2016 Informa UK Limited, trading as Taylor & Francis Group. Recently, there have been numerous insightful applications of zero-sum stochastic differential games in insurance, as discussed in Liu et al. [Liu, J., Yiu, C. K.-F. & Siu, T. K. (2014). Optimal investment of an insurer with regime-switching and risk constraint. Scandinavian Actuarial Journal 2014(7), 583–601]. While there could be some practical situations under which nonzero-sum game approach is more appropriate, the development of such approach within actuarial contexts remains rare in the existing literature. In this article, we study a class of nonzero-sum reinsurance-investment stochastic differential games between two competitive insurers subject to systematic risks described by a general compound Poisson risk model. Each insurer can purchase the excess-of-loss reinsurance to mitigate both systematic and idiosyncratic jump risks of the inter-arrival claims; and can invest in one risk-free asset and one risky asset whose price dynamics follows the famous Heston stochastic volatility model [Heston, S. L. (1993). A closed-form solution for options with stochastic volatility with applications to bond and currency options. Review of Financial Studies6, 327–343]. The main objective of each insurer is to maximize the expected utility of his terminal surplus relative to that of his competitor. Dynamic programming principle for this class of nonzero-sum game problems leads to a non-canonical fixed-point problem of coupled non-linear integral-typed equations. Despite the complex structure, we establish the unique existence of the Nash equilibrium reinsurance-investment strategies and the corresponding value functions of the insurers in a representative example of the constant absolute risk aversion insurers under a mild, time-independent condition. Furthermore, Nash equilibrium strategies and value functions admit closed forms. Numerical studies are also provided to illustrate the impact of the systematic risks on the Nash equilibrium strategies. Finally, we connect our results to that under the diffusion-approximated model by proving explicitly that the Nash equilibrium under the diffusion-approximated model is an (Formula presented.) -Nash equilibrium under the general Poisson risk model, thereby establishing that the analogous Nash equilibrium in Bensoussan et al. [Bensoussan, A., Siu, C. C., Yam, S. C. P. & Yang, H. (2014). A class of nonzero-sum stochastic differential investment and reinsurance games. Automatica50(8), 2025–2037] serves as an interesting complementary case of the present framework