GaInP/GaAs HBTs for high-speed integrated circuit applications

The use of GaInP/GaAs heterojunction bipolar transistors (HBTs) for integrated circuit applications is demonstrated. The discrete devices fabricated showed excellent DC characteristics with low V_ce offset voltage and very low temperature sensitivity of the current gain. For a non-self-aligned device with a 3-μm×1.4-μm emitter area, f_T was extrapolated to 45 GHz and f_max was extrapolated to 70 GHz. The measured 1/f noise level was 20 dB better than that of AlGaAs HBTs and comparable to that of low-noise silicon bipolar junction transistors, and the noise bump (Lorentzian component) was not observed. The fabricated gain block circuits showed 8.5 dB gain with a 3-dB bandwidth of 12 GHz, and static frequency dividers (divide by 4) were operable up to 8 GHz     

Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate

The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode‐particle collision method and cyclic voltammetry, respectively. The influence of Cl^? and NO₃^? anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single‐particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal‐based nanoparticles in general, and copper‐based nanoparticles in particular, are discussed.     

An InGaP/GaAs Merged HBT-FET (BiFET) Technology and Applications to the Design of Handset Power Amplifiers

The last decade has seen GaAs HBTs emerge as the dominant technology in wireless handset power amplifiers. Modern application requirements and size limitations have driven industry leaders towards the co-integration of depletion mode n-FET and GaAs HBT. The merger of Bipolar and FET, or BiFET, gives an additional degree of freedom in the design of advanced power amplifiers independent of a silicon controller. This paper provides an overview of the various techniques that can be used to join the two device technologies and then shows how a merged epitaxial structure, where an FET is formed in the emitter layers of an HBT, combines functional versatility with the high volume manufacturability needed to supply millions of power amplifiers at low cost. A large-signal model of the FET structure is developed which takes into account the unique physics and geometries of the device, including voltage-dependant parameters and charges on all four electrical terminals. Specific handset applications that can benefit or be enabled by BiFET are presented, such as on-off switching, low voltage bias controllers , Auto-Bias power amplifiers, and bias circuits with low or no voltage reference. When npn-only bias circuitry is limited to low voltage reference levels, HBT power amplifiers with BiFET bias stages are shown to have superior RF performance to their npn-only counterparts.     

Demonstration of low-knee voltage high-breakdown GaInP double HBTsusing novel compound collector design

We have demonstrated a heterojunction bipolar transistor using a novel compound collector (CCHBT) design that allows a low-knee voltage and high-breakdown voltage to be obtained simultaneously. The novel aspect of this design is to use a short wide band-gap collector only over a narrow portion of the collector, where the field is highest. This allows support of high fields while maintaining a low overall collector resistance due to the higher mobility of the narrow band-gap material. We demonstrate an offset voltage reduction of about 35% and a knee-voltage reduction of 30%, while increasing both BVCEO and BVCBO by 20 and 27%, respectively, compared to a single heterojunction device of the same collector length     

A packaged broad-band monolithic variable gain amplifierimplemented in AlGaAs/GaAs HBT technology

Broad-band amplifiers find application in fiber-optic communication link and instrumentation or serve as generic components in high-speed electronic test laboratories. With an advanced AlGaAs/GaAs heterojunction bipolar transistor (HBT) technology, we have designed and fabricated broad-band monolithic variable gain amplifiers (VGAs). High-speed packages for the VGAs were carefully designed to minimize insertion and return losses and to suppress undesired package cavity resonances. Accurate and efficient models for the packages were obtained based on experimental data so that their parasitic effects could be considered in the VGA design. The packaged VGAs provided 10-16 dB adjustable gain with approximately ±1 dB gain variations and constant group delay in the DC-26 GHz band, and showed better than 10 dB input/output return losses in the amplifier passband. When the packaged VGAs were inserted in a 30 Gb/s electronic link, error-free operation was achieved for a 2³¹-1 input pseudorandom bit sequence. These VGAs can be used in fiber-optic transmission systems with data rates up to 30 Gb/s     

Determining the effectiveness of HBT emitter ledge passivation byusing an on-ledge Schottky diode potentiometer

A Schottky diode, which contacts the emitter ledge directly, is used as a potentiometer to monitor the effectiveness of the emitter/base junction passivation in GaAs based heterojunction bipolar transistors (HBTs). The function and mechanism of this on-ledge potentiometer are carefully analyzed and modeled. With this apparatus, the emitter ledge potential (V_Ledge) can be measured as a function of the base-emitter bias voltage V_BE. By relating V_Ledge to V_BE. We are capable of quantifying the extent of the ledge depletion down to a few angstroms (<10 Å) in precision. The excellent detectivity of the potentiometer makes it a very powerful tool in the diagnosis of HBT problems in both operation and long-term reliability. These problems have not been detectable or distinguishable with prior techniques     

A broad-band lumped element analytic model incorporating skin effect and substrate loss for inductors and inductor like components for silicon technology performance assessment and RFIC design

We present a broad-band lumped element planar inductor model that is suitable for RFIC design in silicon technologies. We provide extensions of the modeling methodology to similar components such as differential inductors, baluns, and solenoid inductors. The analytic computation of the physics-based model components, incorporating both metal skin effect and substrate loss, is described. The model is validated using measured data from over 200 inductors made with five different silicon back-end process technologies. The physics-based implementation of the model allows its use for determining the optimum process technology characteristics for specific radio frequency integrated circuit (RFIC) designs. The analytical based implementation with lumped elements enables effective integration into a robust CAD system for efficient design of RFIC circuits.     

Design of high-efficiency current-mode class-D amplifiers for wireless handsets

Design considerations are discussed for current-mode class-D (CMCD) microwave power amplifiers. Factors affecting amplifier efficiency are described analytically and via simulation. Amplifiers are reported that incorporate parallel LC resonators alongside the switching transistors. To reduce parasitic resistance, bond-wires were utilized to implement a high Q inductor in the LC resonator. An experimental CMCD amplifier based on GaAs HBTs is reported, with collector efficiency of 78.5% at an output power of 29.5 dBm (0.89 W) at 700 MHz.     

Modulating HBT's current gain by using externally biased on-ledgeSchottky diode [GaAs devices]

The current gain of heterojunction bipolar transistors (HBT's) can be effectively modulated through Schottky diodes that contact the emitter passivation ledge directly. The behavior of the gain modulation is determined by the degree of the emitter ledge depletion. If the ledge is fully depleted, HBT's current gain can be modulated in the whole base-emitter bias voltage (V_BE) range up to 1.6 V. If the ledge is partially depleted, HBT's current gain can be modulated only in the low V_BE range (<1.35 V). This discovery leads to a simple method for monitoring the effectiveness of HBT's emitter ledge passivation and offers new insights to the mechanism of HBT gain degradation. It also creates a four-terminal HBT with an extra ledge electrode biased to control and modulate device's current gain at microwave frequencies     

Application of GaInP/GaAs DHBTs to power amplifiers for wirelesscommunications

Next-generation power amplifiers must operate at lower supply voltages without sacrificing linearity or efficiency. GaInP/GaAs double-heterojunction bipolar transistors with GaInP collectors can improve over GaAs single-heterojunction bipolar transistors (HBTs) in power-amplifier applications, based on lower offset voltage, increased breakdown electric field, and absence of saturation charge storage. To best exploit these characteristics, amplifier architectures that employ HBTs in switching mode can be used