D. Scherrer

Temperature dependent study of the microwave performance of 0.25-/spl mu/m gate GaAs MESFETs and GaAs pseudomorphic HEMTs

We report on the noise figure, associated gain, and the current gain cutoff frequency for comparable 0.25-/spl mu/m gate GaAs MESFETs and GaAs pseudomorphic HEMTs (p-HEMTs) as a function of cryogenic temperature. Contrary to previously published results which suggest that p-HEMTs should have a higher electron velocity and a lower noise figure than MESFETs due to the effects of the two-dimension electron gas (2-DEG), we have experimentally verified that this is not the case. We show clear evidence that the transport properties of the 2-DEG in p-HEMTs do not make a significant contribution to the speed enhancement and noise reduction during high-frequency operation of these devices. It is the fundamental InGaAs material properties, specifically the /spl Gamma/-L valley separation in the conduction band and associated effective mass of the electron in either GaAs or InGaAs channel, which limits the high-field electron velocity and thus the speed and noise performance of the devices.

Temperature dependent study of carbon-doped InP/InGaAs HBT's

We report on a temperature dependent study of the dc and the microwave performance of carbon-doped InP/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistors (HBTs). The turn on voltage increased 114% and the dc current gain decreased 25% as the temperature was reduced from 300 K to 33 K. Under high-current injection, there was a 29% increase in the current gain cutoff frequency of these devices as the temperature was lowered from 300 K to 77 K. By investigating the operation of HBTs at cryogenic temperatures, increased understanding of the mechanisms of carrier transport in these devices can be obtained, and this may lead to improvements in device performance.

Temperature dependence study of two-dimensional electron gas effect on the noise performance of high frequency field effect transistors

We present experimental evidence that the noise figure (NF) and associated gain equal to those achieved with GaAs pseudomorphic high electron mobility transistors (GaAs p-HEMTs) can also be accomplished by ion implanted GaAs metal-semiconductor field-effect transistors (GaAs MESFETs). These measured noise figure results as a function of low temperature for GaAs MESFETs and p-HEMTs clearly suggest that the transport properties of the two-dimensional electron gas in HEMTs and p-HEMTs do not make a significant contribution to the noise reduction at high frequency operation of these devices.<<ETX>>

Low-power performance of 0.5- mu m JFET for low-cost MMIC's in personal communications

The low-power microwave performance of an enhancement-mode ion-implanted GaAs JFET is reported. A 0.5- mu m*100- mu m E-JFET with a threshold voltage of V/sub th/=0.3 V achieved a maximum DC transconductance of g/sub m/=489 mS/mm at V/sub ds/=1.5 V and I/sub ds/=18 mA. Operating at 0.5 mW of power with V/sub ds/=0.5 V and I/sub ds/=1 mA, the best device on a 3-in wafer achieved a noise figure of 0.8 dB with an associated gain of 9.6 dB measured at 4 GHz. Across a 3-in wafer the average noise figure was F/sub min/=1.2 dB and the average associated gain was G/sub a/=9.8 dB for 15 devices measured. These results demonstrate that the E-JFET is an excellent choice for low-power personal communication applications.<<ETX>>

Eye‐diagram and scattering parameter characterization of superconducting and gold coplanar transmission lines

We report the gigahertz experimental results of time and frequency performance on YBCO high‐temperature superconductor and gold coplanar transmission lines. An on‐wafer direct probing measurement system was used to collect data at cryogenic temperatures on both YBCO and gold coplanar lines. The insertion loss of the 6 cm lines at a frequency of 2.5 GHz was measured to be −0.03 dB for the superconducting line compared to −10.4 dB for the gold line at 80 K. Eye‐diagram measurements were performed on the packaged lines and show the correlation between the insertion loss of the line and the attenuation of a pseudorandom bit sequence. The measured eye height was 170 mV for the YBCO compared to 90 mV for a gold line at 1 Gbit/s and a temperature of 77 K for the packaged 6 cm lines.

Accurate passive component models in coplanar waveguide for 50 GHz MMICs

Accurate circuit models for several passive components in coplanar waveguide have been developed. These models utilize lumped and distributed circuit elements available in computer-aided design software packages and have element values that are derived from measured S-parameter data, geometrical data and physical process parameters. This work discusses the development of the models and verifies their accuracy by comparing measured and modeled S-parameters to 50 GHz.

Microwave performance of low-power ion-implanted 0.25-micron gate GaAs MESFET for low-cost MMIC's applications

Low-power microwave performance of an enhancement mode) (E-mode ion-implanted GaAs MESFET is reported. The 0.25- mu m*100- mu m E-MESFET has a threshold voltage of V/sub th/=0.0 V. At 1.0-mW operation of power with a bias condition of V/sub ds/=0.5 V and I/sub ds/-2 mA, a noise figure of 0.85 dB with an associated gain of 15 dB was measured at 4 GHz. These results demonstrate that the GaAs E-MESFET is an excellent choice for low-power personal communication applications.<<ETX>>

Optimal noise matching of 0.25 micron gate GaAs MESFETs for low power personal communications receiver circuit designs

0.25 /spl mu/m GaAs MESFETs are shown to be excellent device candidates for low current, low noise receiver circuits in personal communicators. The measured low current performance of ion-implanted 0.25 /spl mu/m gate FETs is reported for device gate widths of 100 /spl mu/m and 200 /spl mu/m and device bias conditions 0.5 V<V/sub ds/<1.5 V and 0.2 mA<I/sub ds/<5 mA. The 0.25 /spl mu/m/spl times/200 /spl mu/m device achieved a noise figure of 0.69 dB and associated gain of 12.4 dB at 2 GHz while drawing 1 mA of drain current. The matching characteristics and equivalent circuit models of these devices under low current bias conditions are also discussed.<<ETX>>

Noise performance of low power 0.25 micron gate ion implanted D-mode GaAs MESFET for wireless applications

We report on the noise performance of low power 0.25 /spl mu/m gate ion implanted D-mode GaAs MESFETs suitable for wireless personal communication applications. The 0.25 /spl mu/m/spl times/200 /spl mu/m D-mode MESFET has a f/sub t/ of 18 GHz and f/sub max/ of 33 GHz at a power level of 1 mW (power density of 5 mW/mm). The noise characteristics at 4 GHz for the D-mode MESFET are F/sub min/=0.65 dB and G/sub assoc/=13 dB at 1 mW. These results demonstrate that the GaAs D-mode MESFET is also an excellent choice for low power personal communication applications.<<ETX>>

Noise and gain comparison of 0.25 μm gate MESFETs and PHEMTs for low power wireless communication circuits

Abstract We compare the low power, low noise performance of 0.25 μm ion implanted MESFETs and epitaxially grown P HEMTs fabricated with the same geometry in order to identify the suitability of these technologies for the manufacture of hand-held personal communications products. We examine the microwave performance of the devices under low power operating conditions and we analyse the critical factors contributing to the noise performance. In the high current regime we have found that the MESFETs and P HEMTs have equivalent noise figures and gains at the bias point, which results in the lowest noise figure ( V ds = 1.5 V and I ds = 14 mA). Under low power bias, the P HEMT shows several performance advantages over the MESFET, including higher associated gain, lower R n , and lower / vbΓ opt / vb . We believe these advantages result from the sharpness of the doping profile in the epitaxial material and the rapid decrease in carrier concentration at the buried heterojunction, rather than the two-dimensional electron gas effect. Under 1 mW of d.c. bias ( V ds = 0.5 V, I ds = 2 mA) at 6 GHz, the MESFETs noise figure was 0.5 dB and its associated gain was 8 dB. The noise figure of the P HEMT for the same conditions was 0.6 dB and its associated gain was 10 dB.