III-V Heterojunction Bipolar Transistors Research Articles

Methods for Extracting the Temperature- and Power-Dependent Thermal Resistance for SiGe and III-V HBTs From DC Measurements: A Review and Comparison Across Technologies

Many different methods have been proposed in the literature for the extraction of the thermal resistance of heterojunction bipolar transistors (HBTs). This review presents a detailed evaluation and discussion of several widely used methods. Special emphasis is put on a generalized analysis of the underlying assumptions, suitable operating point range, and necessary measurement effort of each method. The accuracy of each method is determined by applying it to data based on circuit simulations of advanced SiGe and III-V HBT technologies. Experimental data from those technologies are used to highlight practical issues. A guideline for the selection of the most suitable method in practice is also given.

1-D Drift-Diffusion Simulation of Two-Valley Semiconductors and Devices

A two-valley formulation of 1-D drift-diffusion transport is presented that takes the coupling between the valleys into account via a new approximation for the nonlocal electric field. The proposed formulation is suitable for the simulation of III-V heterojunction bipolar transistors as opposed to formulations that employ the single electron gas approximation with a modified velocity-field model, which also causes convergence problems. Based on Boltzmann transport equation simulations, model parameters of the proposed two-valley formulation are given for GaAs, InP, InAs, and GaSb at room temperature. Applications of the new formulation are also demonstrated.

A Closed-Form Solution for the Low-Current Collector Transit Time in Group IV and Group III-V HBTs

In certain types of heterojunction bipolar transistors (HBTs), the carrier transit time associated with the base-collector (BC) space-charge region constitutes a significant contribution to the total transit time. In many compact models, the low-current BC transit time is lumped in with the total low-current transit time and often assumed to be constant—dependent only on the collector width and material saturation velocity. This assumption, however, is insufficient for modeling high-voltage Si-based HBTs as well as for III-V HBTs, where the negative differential mobility (NDM) effect can become relevant in high-speed low-power circuits. This paper presents a closed-form solution for the low-current collector transit time based on a novel accurate analytical velocity-field formulation, covering both group IV and group III-V semiconductor materials. The new solution includes the NDM effect and is suitable for implementation in compact models, and its relevance and accuracy are demonstrated for both TCAD simulated and measured data.

Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide

A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation.

Radiation Effects in SiGe Technology

Silicon-Germanium (SiGe) technology effectively merges the desirable attributes of conventional silicon-based CMOS manufacturing (high integration levels, at high yield and low cost) with the extreme levels of transistor performance attainable in classical III-V heterojunction bipolar transistors (HBTs). SiGe technology joins together on-die high-speed bandgap-engineered SiGe HBTs with conventional Si CMOS to form SiGe BiCMOS technology, including all the requisite RF passive elements and multi-level thick-Al metalization required for high-speed circuit design. Such an silicon-based integrated circuit technology platform presents designers with an ideal division of labor for realizing optimal solutions to many performance-constrained mixed-signal (analog + digital + RF) systems. The unique bandgap-engineered features of SiGe HBTs enable several key merits with respect to operation across a wide variety of so-called “extreme environments”, potentially with little or no process modification, ultimately providing compelling advantages at the circuit and system level, across a wide class of envisioned commercial and defense applications. Here we give an overview of this interesting field, focusing primarily on the intersection of SiGe HBTs, and circuits built from them, with radiation-intense environments such as space.

A thermal-fully hydrodynamic model for semiconductor devices and applications to III-V HBT simulation

Because of the interaction between self-heating and hot carriers effects, neither isothermal nor conventional macrothermal models are adequate for the simulation of state-of-the-art power devices; instead, a detailed electro-thermal model accounting for nonstationary transport, such as the Thermal-Fully Hydrodynamic (T-FH) model, is required. We apply a one-dimensional (1-D) implementation of such a model to the simulation of AlGaAs/GaAs and InP/InGaAs Heterojunction Bipolar Transistors (HBTs), comparing the results with those provided by simplified models, and highlighting how deeply both nonlocal transport and self-heating affect the predicted device performance. The importance of the convective terms is assessed, and a new nonthermal mechanism for the output Negative Differential Resistance (NDR) is proposed.

Measurement and comparison of 1/f noise and g-r noise in silicon homojunction and III-V heterojunction bipolar transistors

This paper experimentally determines and compares the 1/f noise and the g-r noise, as components of the base noise current spectral density, in Si homojunction and III-V heterojunction bipolar transistors (HBTs) in common-emitter configuration. The noise spectra for each of these devices are obtained as functions of the base bias current (I/sub B/), and the 1/f noise has been found to depend on I/sub B/ as I/sub B//sup /spl gamma//, where /spl gamma//spl sim/1.8 for the silicon BJT's and InP/InGaAs HBT's with high current gains (/spl beta//spl sim/50), and /spl gamma//spl sim/1.1 for the AlGaAs/GaAs HBTs with low current gains (4</spl beta/<12). The nearly constant current gain and the near square-law and inverse-square emitter area dependence of 1/f noise in silicon devices are indicative of the dominant base bulk recombination nature of this noise. The 1/f noise in the InP based HBTs has been found to be lowest among all the devices we have tested, and its origin is suggested to be the base bulk recombination as in the Si devices. For the AlGaAs/GaAs HBTs, the low current gain and the near unity value of /spl gamma/, arise most likely due to the combined effects of surface, bulk, and depletion region recombinations and the base-to-emitter injection. The dependence of the 1/f noise on the base current density in the devices tested in this work, and those tested by others are compared to find out which HBT's have achieved the lowest level of 1/f noise.

Scaled AlInAs/InGaAs and InP/InGaAs heterostructure bipolar transistors

Summary form only given. The authors report on Al/sub 0.48/In/sub 0.52/As/In/sub 0.53/Ga/sub 0.47/ and InP/In/sub 0.53/Ga/sub 0.47/As HBTs (heterojunction bipolar transistors), which demonstrate near-ideal lateral scaling and ultrahigh-speed performance. Abrupt emitter-base junction are used to realize high-energy electron injection and nonequilibrium transport in the base and collection depletion region. Current gains of beta =162 and 122 have been realized in AlInAs/InGaAs transistors with emitter stripe widths of 50 and 0.6 mu m, respectively. Microwave characteristics of the InP/InGaAs HBTs show and f/sub T/=165 GHz, while preliminary results of the AlInAs/InGaAs devices show f/sub T/=72 GHz, which is limited by the parasitics. Also demonstrated is the first successful high-speed scaling of III-V HBTs by achieving f/sub T/>100 GHz in transistors with emitter stripe widths of less than 0.6 mu m. The high performance is due to the large conduction band Gamma -L (0.55 eV) and Gamma -X (1.15 eV) separation in the InGaAs base and collector. >