GaAs High Electron Mobility Transistor Research Articles

Reactive ion etching of via holes for GaAs high electron mobility transistors and monolithic microwave integrated circuits using Cl2/BCl3/Ar gas mixtures

A process for through-the-wafer via hole connections to each individual source contact for monolithic microwave and millimeter wave integrated circuits and power high electron mobility transistors has been developed using reactive ion etching in Cl2/BCl3/Ar gas mixtures. Placing vias in this manner eliminates the need for source airbridges, which minimizes source inductance and results in increased gain and efficiency. The GaAs etch rate and resultant etch profiles have been studied as functions of bias voltage, gas mixture, flow rate, via mask dimension, and etch time.

Large Area and Highly Uniform MOVPE Growth for AlGaAs / GaAs HEMT LSIs

A metallorganic vapor phase epitaxial (MOVPE) technique is used to produce successfully the epitaxial layer of a selectively doped high electron mobility transistor (HEMT) structure. We have developed a method for mass producing HEMT‐LSIs (large‐scale integration). Our low pressure barrel reactor can grow twelve 3‐inch wafers simultaneously using a wafer rotation system. The heterointerface fluctuates by less than several angstroms over the entire wafer. Their electrical characteristics are excellent and the distribution in both layer thickness and donor concentration satisfy the demands for LSI applications. We used photolithography to fabricate HEMT devices with 0.6 μm long gates. We applied the MOVPE technique to a 64 kbit HEMT SRAM and obtained a typical address access time of 1.2 ns at a power dissipation of 5.9 W.

Étude des pièges dans les transistors à haute mobilité électronique sur GaAs à l'aide de la méthode dite de “relaxation isotherme”. Corrélation avec les anomalies de fonctionnement

Trap-related parasitic effects penalizing the GaAs high electron mobility transistor have been studied by means of isothermal relaxation experiment. Basic principles together with improvements are briefly described. Once the method validated, typical cases are reported. It appears as a usefull investigation tool supporting the choice of high speed electron device technologies to be introduced into systems

Microwave monolithic analogue frequency divider with GaAs HEMT

AbstractAn analogue frequency divider implemented with a new GaAs high electron mobility transistor (HEMT) MMIC technology is presented. This frequency divider is based on the frequency regeneration principle. The circuit operates in a frequency division bandwidth of 700 MHz at — I dBm incident input power level around 12.8 GHz. © 1992 John Wiley & Sons, Inc.

High-power V-band pseudomorphic InGaAs HEMT

The author's present the DC and RF power performance of planar-doped channel InGaAs high-electron-mobility transistors (HEMTs). The planar-doped channel (PDC) pseudomorphic GaAs HEMT with 400 mu m of gate width exhibited an output power of 184 mW, corresponding to 460 mW/mm, with 4.6-dB saturation gain and 25% power-added efficiency at 55 GHz. Although higher power density is possible, the authors have designed the device to operate at less than 500 mW/mm for thermal and reliability reasons. Devices with unit gate finger widths ranging from 30 to 50 mu m were fabricated and characterized, with no performance degradation observed from using the longer gate fingers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Heavy ion total fluence effects in GaAs devices

Heavy ion radiation effects were studied in GaAs FETs, monolithic microwave integrated circuits (MMICs), and high-electron-mobility transistors (HEMTs). Degradation of GaAs FETs, MMICs, and HEMTs occurred at about 10/sup 9/ cm/sup -2/ for 14.5-MeV Si and at 10/sup 12/ cm/sup -2/ for 2-MeV protons. Carrier removal resulting from displacement damage in the active channel, or in the doping layer in the case of HEMTs, is the primary reason for the decrease in drain current and gain and the increase in noise figure. Decrease in mobility is also a contributing factor. HEMTs were found to degrade in gain and noise figure at higher levels of irradiation, primarily because of the initial higher dopant concentration in the AlGaAs N/sup +/ doping layer.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modeling and simulation of interconnection delays and crosstalks in high-speed integrated circuits

A computer model for n parallel microstrip lines is developed for circuit simulation. This model for the lossy transmission line system can be readily implemented into circuit simulators and can accurately simulate the delay and crosstalk effects of interconnects in high-speed integrated circuits. Modal analysis is applied to decouple the n-coupled-line system into n independent lines, and the characteristic solutions of telegraph equations are represented by a set of simple time-varying equivalent circuits. The model has been implemented in a general-purpose circuit simulator, iSMILE, which is compatible with SPICE. Simulation results on propagation delay times and crosstalk are presented for high-speed GaAs HEMT (high-electron-mobility transistor) integrated circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Surface superlattices and quasi-one-dimensional conductors in GaAs HEMTs: how best to compare theory and experiment?

The authors discuss evidence of (1) electron standing waves forming underneath a 2000-AA period Ti/Au Schottky grid or grating incorporated as a gate into a GaAs HEMT (high-electron-mobility transistor) structure, and (2) modulation of the scattering time due to intersubband scattering in an array of approximately 100 parallel wires of 400-AA width formed by laterally patterning a GaAs/GaAlAs heterostructure. The authors show how knowledge of the electron group velocity along with a scattering rate derived from Fermi's golden rule can explain the observed effects. They compare the mobility modulation from intersubband scattering to the well-known prediction of Sakaki for increased mobility in quasi-one-dimensional wire due to the finite range of the scatterers. By first solving for the density of states and conductivity in a one-dimensional periodic potential, the authors show how to incorporate energy level broadening due to elastic and inelastic scattering, temperature broadening, and an increase in the dimensionality of the device by convolving with various known functions.

DC and transmission line models for a high electron mobility transistor

Two improved DC models are developed to describe the output I-V (current-voltage) characteristics and small-signal parameters of a GaAs high-electron-mobility transistor (HEMT). A simple analytical, nonlinear, charge-control model for a two-dimensional electron gas is introduced and included in one of the DC models. The HEMT is modeled as a transmission line for the microwave-frequency AC analysis, and its microwave performance is predicted by the parameters obtained from fitting DC characteristics. Both DC and AC model predictions show a good agreement with experimental results for a 0.3- mu m GaAs HEMT. >

Analysis of Optically Controlled Microwave/Millimeter-Wave Device Structures

Light-induced voltage and the change in the source-to-drain channel current under optical illumination higher than the semiconductor band gap for GaAs MESFET, InP MESFET, Al/sub 0.3/Ga/sub 0.7/As/GaAs high electron mobility transistor (HEMT), and GaAs permeable base transistor (PBT) are analytically obtained. The GaAs PBT and GaAs MESFET have higher sensitivity than the InP MESFET. However, the Al/sub 0.3/Ga/sub 0.7/As/ GaAs HEMT is observed to have the highest sensitivity. Variations in the small-signal parameters, such as channel conductance, gate-to-source capacitance, and transconductance, as well as transient parameters, such as switching time and power-delay product, of GaAs MESFET with illumination are computed. The computed capacitance and transconductance are compared with the experimentally obtained values and are found to be in fair agreement. Based on these results, the design considerations for an optically controlled MESFET switch are discussed. Finally, variation in device parameter due to optical illumination and its effect on the cutoff frequencies f/sub T/ and f/sub max/ are also investigated.

New technology towards GaAs LSI/VLSI for computer applications

For future large-scale computer applications, new device technologies towards GaAs LSI/VLSI have been developed: self-aligned fully implanted planar GaAs MESFET technology and high electron mobility transistor (HEMT) technology by molecular beam epitaxy (MBE). The self-aligned GaAs MESFET logic with 1.5-µm gate length exhibits a minimum switching time of 50 ps and the lowest power-delay product of 14.5 fJ at room temperature. The enhancement/depletion (E/D) type direct coupled HEMT logic has achieved a switching time of 17.1 ps with 1.7-µm gate length at liquid nitrogen temperature and more recently a switching time of 12.8 ps with 1.1-µm gate HEMT logic, which exceeds the top speed of Josephson Junction logic and shows the highest speed of any device logic ever reported. Optimized system performances are also projected to system delay of 200 ps at 10-kilogate integration with GaAs MESFET VLSI, and 100 ps at 100-kilogate with HEMT VLSI. These values of system delay correspond to the computer performance of over 100 million instructions per second (MIPS).

New Technology Towards GaAs LSI/VLSI for Computer Applications

For future large-scale computer applications, new device technologies towards GaAs LSI/VLSI have been developed self-aligned fully implanted planar GaAs MESFET technology and high electron mobility transistor (HFMT) technology by molecular beam epitaxy (MBE). The self-aligned GaAs MESFET logic with 1.5-µm gate length exhibits a minimum switching time of 50 ps and the lowest power-delay product of 14.5 fJ at room temperature. The enhancement/depletion (E/D) type direct coupled HEMT logic has achieved a switching time of 17.1 ps with 1.7-µm gate length at liquid nitrogen temperature and more recently a switching time of 12.8 ps with 1.1-µm gate HEMT logic, which exceeds the top speed of Josephson Junction logic and shows the highest speed of any device logic ever reported. Optimized system performances are also projected to system delay of 200 ps at 10-kilogate integration with GaAs MESFET VLSI, and 100 ps at 100-kilogate with HEMT VLSI. These values of system delay correspond to the computer performance of over 100 million instructions per second (MIPS).