InGaAs-InP metamorphic DHBTs grown on GaAs with lattice-matched device performance and f(T), f(max) > 268 GHz

InP-In0.53Ga0.47As-InP double heterojunction bipolar transistors (DHBTs) were grown on a GaAs substrate using a metamorphic buffer layer and then fabricated. The metamorphic buffer layer is InP--employed because of its high thermal conductivity to minimize device heating. An f(t) and f(max) of 268 and 339 GHz were measured, respectively-both records for metamorphic DHBTs. A 70-nm SiO2 dielectric sidewall was deposited on the emitter contact to permit a longer InP emitter wet etch for increased device yield and reduced base leakage current. The dc current gain beta is approximate to35 and BV,CEO = 5.7 V. The collector leakage current Icbo is 90 pA at Vcb = 0.3 V. These values of f(t), f(max), I-cbo, and beta are consistent with InP based DHBTs of the same layer structure grown on a lattice-matched InP substrate

InGaAs-InP DHBTs for increased digital IC bandwidth having a 391-GHz f(T) and 505-GHz f max

InP-In0.53Ga0.47As-InP double heterojunction bipolar transistors (DHBT) have been designed for use in high bandwidth digital and analog circuits, and fabricated using a conventional mesa structure. These devices exhibit a maximum 391-GHz f(t), and 505-GHz f(max), which is the highest f(t) reported for an InP DHBT--as well as the highest simultaneous f(t) and f(max) for any mesa HBT. The devices have been aggressively scaled laterally for reduced base-collector capacitance Ccb. In addition, the base sheet resistance rho(s) along with the base and emitter contact resistivities rho(c) have been lowered. The DC current gain beta is approximate to 36 and BV,CEO = 5.1 V. The devices reported here employ a 30-nm highly doped InGaAs base, and a 150-nm collector containing an InGaAs-InAlAs superlattice grade at the base-collector junction. From this device design we also report a 142-GHz static frequency divider (a digital figure of merit for a device technology) fabricated on the same wafer. The divider operation is fully static, operating from f(clk) = 3 to 142.0 GHz while dissipating approximate to 800 mW of power in the circuit core. The circuit employs single-buffered emitter coupled logic (ECL) and inductive peaking. A microstrip wiring environment is employed for high interconnect density, and to minimize loss and impedance mismatch at frequencies > 100 GHz

InGaAs-InP mesa DHBTs with simultaneously high f(T) and f(max) and low C-cb/I-c ratio

We report an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370-GHz f(t) and 459-GHz f(max), which is to our knowledge the highest f(tau)reported for a mesa InP DHBT--as well as the highest simultaneous f(t) and f(max) for any mesa HBT. The collector semiconductor was undercut to reduce the base-collector capacitance, producing a Ccb/Ic ratio of 0.28 ps/V at Vcb = 0.5 V. The BV,CEO is 5.6 V and the devices fail thermally only at > 18 mW/um^2, allowing dc bias from J(e) = 4.8 mA/um^2 at Vce = 3.9 V to J(e) = 12.5 mA/um^2 at Vce = 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

Hypoxia inhibits the migratory capacity of human monocyte-derived dendritic cells

Hypoxia, a prominent characteristic of inflammatory tissue lesions and solid tumour microenvironments, is a crucial stimulus capable of modulating the expression of specific genes involved in leucocyte recruitment. Although studies have shown that hypoxia can affect leucocyte migration by influencing the expression of migration-related genes, such as matrix metalloproteinases (MMP) and their endogenous tissue inhibitors of matrix metalloproteinases (TIMP), it remains unclear whether hypoxia can affect the migration of dendritic cells (DC). In this study, we showed that human monocyte-derived DC under hypoxic conditions in a transwell system have significantly reduced migratory capacity compared to normoxic controls. A moderate phenotypic change of hypoxic DC was observed. In hypoxic DC, we detected a twofold increase in TIMP-1 transcript levels, and downregulated expression of MMP-9 and membrane type 1-MMP genes by threefold and 17-fold, respectively. Our results suggest that hypoxia may inhibit DC migratory activity by regulating the balance between MMP and TIMP gene expression. © 2005 Australasian Society for Immunology Inc.link_to_subscribed_fulltex

Millimeter-wave power amplifiers

This book provides a detailed review of millimeter-wave power amplifiers, discussing design issues and performance limitations commonly encountered in light of the latest research. Power amplifiers, which are able to provide high levels of output power and linearity while being easily integrated with surrounding circuitry, are a crucial component in wireless microwave systems. The book is divided into three parts, the first of which introduces readers to mm-wave wireless systems and power amplifiers. In turn, the second focuses on design principles and EDA concepts, while the third discusses future trends in power amplifier research. The book provides essential information on mm-wave power amplifier theory, as well as the implementation options and technologies involved in their effective design, equipping researchers, circuit designers and practicing engineers to design, model, analyze, test and implement high-performance, spectrally clean and energy-efficient mm-wave systems