G.I. Ng

Design and experimental characteristics of strained In/sub 0.52/Al/sub 0.48/As/In/sub x/Ga/sub 1-x/As (x>0.53) HEMTs

Strained In/sub 0.52/Al/sub 0.48/ As/In/sub x/Ga/sub 1-x/As (x>0.53) HEMTs (high electron mobility transistors) are studied theoretically and experimentally. A device design procedure is reported that is based on band structure and charge control self-consistent calculations. It predicts the sheet carrier density and electron confinement as a function of doping and thickness of layers. The DC performance at 300 K is presented. Wafer statistics demonstrate improvement of device characteristics with excess indium in the channel (g/sub m,/ /sub intr/=500 and 700 mS/mm for x=0.60 and 0.65). Microwave characterization shows the f/sub T/ improvement (f/sub T/=40 and 45 GHz for x=0.60 and 0.65, respectively) and the R/sub ds/ limitations of the 1- mu m-long-gate HEMTs. >

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 >

An analytical approach to the capacitance-voltage characteristics of double-heterojunction HEMTs

The two-dimensional electron gas concentration and capacitance in AlGaAs/GaAs/AlGaAs double-heterojunction high-electron-mobility transistors (DH-HEMTs) are calculated as a function of gate voltage using simple iterative solutions of analytical equations. The results show very good agreement with experimental data, as well as with characteristics predicted by complex numerical methods. The calculations are extended to predict the capacitance-voltage characteristics in the presence of parasitic conduction when the gate does not fully control the two-dimensional gas. The developed charge control and capacitance models are easy and inexpensive to run. They are therefore very useful for microwave circuit designs. Furthermore, they can be used for performance prediction and design optimization of DH-HEMTs. The influence of technological parameters, such as layer thickness and aluminum composition, on device performance are presented. >

Experimental characteristics and performance analysis of monolithic InP-based HEMT mixers at W-band

Experimental characteristics of monolithic InAlAs/InGaAs HEMT mixers are presented together with a theoretical analysis. Experiments at W-band show a maximum conversion gain of 0.9 dB with 2 dBm of LO power level. This is the first demonstration of a monolithic HEMT mixer with conversion gain at W-band. The conversion gain dependence on LO power, RF frequency and gate bias is measured and compared with the theoretical predictions. Good agreement between the theory and experiment could be found. >

Study of the consequence of excess indium in the active channel of InGaAs/InAlAs high electron mobility transistors on device properties

A study of the properties of In0.52Al0.48As/In0.53+xGa0.47−xAs high electron mobility transistors is carried out for 0%, 7%, and 12% excess In values in the channel. Theoretical analysis shows that the enhanced In causes a biaxial compressive strain of 0.49% to 0.84% in the channel, increases the band‐edge discontinuity from 0.437 to 0.500 eV, and reduces the carrier mass by 6%. Experimental characterizations support the theoretical predictions by demonstrating an increase of mobility from 9900 to 11 200 cm2/V s at 300 K, and a transconductance enhancement from 160 to at least 230 mS/mm.

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>>

High efficiency monolithic Ka-band oscillators using InAlAs/InGaAs HEMTs

The performance of monolithic integrated oscillators using submicron InAlAs/InGaAs HEMTs (high electron mobility transistors) at 35 GHz is presented. Two different types of feedback schemes were employed showing distinct bias tuning features. A large-signal analysis was performed to analyze their power characteristics. The dual feedback oscillator had an output power of 8.2 mW and showed a high DC-to-RF efficiency of 36% at 35.6 GHz.<<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>>