M. Tutt

Characteristics of strained In/sub 0.65/Ga/sub 0.35/As/In/sub 0/./sub 52/Al/sub 0/./sub 48/As HEMT with optimized transport parameters

The DC and microwave performance of a strained In/sub 0/./sub 65/Ga/sub 0/./sub 35/As/In/sub 0/./sub 52/A1/sub 0/./sub 48/As HEMT (high-electron-mobility transistors) is reported. Its design is based on theoretical and experimental studies including low- and high-field transport characterization of heterostructures with different strains. The intrinsic DC transconductance and cutoff frequence of 1.4- mu m-long gate HEMTs are 574 mS/mm and 38.6 GHz, respectively. The increased indium (In) composition in the channel enhances the drift velocity from 1.35*10/sup 7/ to 1.55*10/sup 7/ cm/s at 300 K.<<ETX>>

Low-frequency noise characteristics of lattice-matched (x=0.53) and strained (x>0.53) In/sub 0.52/Al/sub 0.48/As/InxGa/sub 1-/xAs HEMT's

Extensive bias-dependent and temperature-dependent low-frequency (LF) noise measurements were performed on lattice-matched and strained In/sub 0.52/Al/sub 0.48/As/In/sub x/Ga/sub 1-x/As(0.53 >

Low frequency noise characteristics of self-aligned AlGaAs/GaAs power heterojunction bipolar transistors

The low frequency noise characteristics of modern self-aligned AlGaAs/GaAs power HBTs have been studied as a function of bias, temperature, frequency, and circuit topology. The devices have a 1/f/sup /spl gamma// behavior between 10 Hz and 100 Hz with 0.78/spl les//spl gamma//spl les/1.65. Strong deviation from 1/f/sup /spl gamma// is measured at higher frequencies due to trapping. The bias dependence of the collector noise ranged from I/sub C//sup 1.5/-I/sub C//sup 2.6/, while that for the base noise ranges from I/sub B//sup 0.7/-I/sub B//sup 2.5/. In all cases the collector noise is greater than the base noise. The base noise is apparently dominated by surface recombination noise and generation-recombination (G-R) noise. The collector noise is due to recombination mechanisms and G-R noise. The activation energy (E/sub a/) of the most significant trap is approximately 0.58 eV. The noise of the devices tested was found to be dominated by material and fabrication related mechanisms and not by fundamental mechanisms. >

Tradeoff between 1/f noise and microwave performance in AlGaAs/GaAs heterojunction bipolar transistors

The 1/f noise characteristics and microwave gain of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) have been investigated as a function of surface passivation ledge length. These measurements clearly demonstrate that the ledge length imposes a tradeoff between the 1/f noise and microwave power gain performance. Compared to a conventional unpassivated self-aligned HBT, HBTs with 0.4 and 1.1 /spl mu/m ledge lengths improve the equivalent input base noise current spectral density at 100 Hz by as much as 2 dB and 6.5 dB, respectively; while degrading the maximum available gain at 18 GHz by 0.3 dB and 2.4 dB, respectively. >

Improved strained HEMT characteristics using double-heterojunction In/sub 0.65/Ga/sub 0.35/As/In/sub 0.52/Al/sub 0.48/As design

The DC and microwave properties of strained In/sub 0.65/Ga/sub 0.35/As/In/sub 052/Al/sub 0.48/As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1*150- mu m/sup 2/ long-gate HEMTs, the measured cutoff frequency f/sub T/ and maximum frequency of oscillation f/sub max/ are as high as 37 and 66 GHz, respectively.<<ETX>>

W-band monolithic mixer using InAlAs/InGaAs HEMT

A W-band monolithic mixer is designed and fabricated using InAlAs/InGaAs HEMT technology. The advantages of this material system compared with AlGaAs/GaAs are: (i) larger conduction band discontinuity (0.5 eV versus 0.24 eV for AlGaAs/GaAs) and therefore better carrier confinement, (ii) higher low-field mobility, and (iii) higher peak velocity. The combination of these features results in a better performance and operation capability in the submillimeter wave range. The design procedure and the circuit performance are described. A very low LO (local oscillator) power requirement is demonstrated with 13.5-dB conversion loss and only -6 dBm LO drive at 95 GHz.<<ETX>>

Reliability issues of InAlAs/InGaAs high-electron-mobility transistors

The effects of thermally stressing submicron In/sub x/Ga/sub 1-x/As/InAlAs/InP (x>or=0.53) HEMTs for storage periods of up to 100 h at 200 degrees C are discussed. DC characteristics are found to degrade. I/sub DSS/ decreased from 299 mA/mm to 182 mA/mm. G/sub m/ decreased from 513 mS/mm to 209 mS/mm. Decreases in microwave performance were also measured. f/sub T/ and f/sub max/ decreased by more than 30% and 20%, respectively. Evidence indicates that changes in the channel/buffer interface and layers manifested by the presence of additional trapping are responsible for this. Measurements of ohmic contacts show an increase from 0.19 Omega -mm to 0.26 Omega -mm. Results of X-ray analysis and Hall characterization are presented.<<ETX>>

180 GHz InAlAs/InGaAs HEMT monolithic integrated frequency doubler

The design, monolithic microwave integrated circuit (MMIC) implementation, and testing of a 180 GHz doubler based on InP-HEMT (high electron mobility transistor) technology is reported. Doublers were fabricated using submicron (0.1 mu m) InAlAs/InGaAs HEMTs. A simplified harmonic content study was employed in order to understand the power characteristics in HEMT doublers. The experimental conversion loss followed the predicted performance and showed a minimum conversion loss of 6 dB at 0 dBm input power.<<ETX>>

Gate-recess and device geometry impact on the microwave performance and noise properties of 0.1 mu m InAlAs/InGaAs HEMT's

A study in which the deep recess was found to be essential in order to maintain a high gate aspect ratio and thus larger G/sub m/G/sub ds/ and C/sub gs//C/sub gd/ ratios is described. This ensures a high power gain and high f/sub max/ which is a figure of merit in microwave circuit operation. Also, proper recessed devices show less microwave noise and broader noise minima. The optimum recess for both microwave and noise performance was found to be around I/sub dss/ of 500 mA/mm for the HEMT and showed f/sub max/ of 217 GHz, f/sub T/ of 173 GHz, and a minimum noise figure of 0.6 dB. The device geometry effect was investigated, and the degradation of the device performance due to the parasitics was found for small gate width devices. Large gate width devices were limited in high frequency performance due to the high gate metal resistance. Overall, an appropriate recess, aspect ratio, and device periphery must be selected for optimum microwave performance.<<ETX>>

Automated On-Wafer Noise and Load Pull Characterization Using Precision Computer Controlled Electromechanical Tuners

A wafer probing system capable of both noise, and load and source pull measurements is described. The system is based on precision computer controlled electromechanical tuners. Sophisticated system software controls calibration, measurements, data analysis and display. Results of measurements of submicron In-GaAs/InAlAs/InP HEMTs and GaAs MESFETs are presented.