A resistor temperature noise model for FETs has been successfully applied to extrinsic FETs to predict the frequency dependence of minimum noise figure F/sub min/ and associated gain G/sub Aopt/. The model gives a fixed relationship between F/sub min/ and G/sub Aopt/ with one fitting parameter T/sub d/. An extensive comparison to published results shows that the majority of FETs can be modeled with effective T/sub d/ values (the temperature of the output resistor) between 300 and 700 K for all of the frequencies (8 to 94 GHz), gate lengths (0.8 to 0.1 mu m), and material types examined. The analysis shows that InP-based MODFETs exhibit significantly lower F/sub min/ and higher G/sub Aopt/ than conventional and pseudomorphic GaAs-based MODFETs of the same gate length. The results suggest a high F/sub max/ is a key factor for low noise figure. >

A temperature noise model for extrinsic FETs

Significant advances in the development of high electron mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (h/spl nu//k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting-insulator-superconducting (SIS) front-ends in the 1-100 GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's is accurate and repeatable device measurements at cryogenic temperatures. A cryogenic on-wafer noise and scattering parameter measurement system has been developed to provide a systematic investigation of HEMT noise characteristics. In addition, an improved parameter extraction technique has been developed to help understand the relationship between device structure and LNA performance.

Development of accurate on-wafer, cryogenic characterization techniques

The design details and measurement results for a cooled L-band (1 to 2 GHz) balanced high electron mobility transistor (HEMT) amplifier are presented. The amplifier uses commercially available packaged HEMT devices (Fujitsu FHR02FH). At a physical temperature of 12 K, the amplifier achieves noise temperatures between 3 and 6 K over the 1 to 2 GHz band. The associated gain is approximately 20 dB.

A cooled 1- to 2-GHz balanced HEMT amplifier

The performance characteristics of InP-based pseudomorphic MODFETs with varying the In composition (0.53 >

Characteristics of 0.8- and 0.2- mu m gate length In/sub x/Ga/sub 1-x/As/In/sub 0.52/Al/sub 0.48/As/InP (0.53<or=x<or=0.70) modulation-doped field-effect transistors at cryogenic temperatures

The design details and measurement results for a cooled 1-GHz-bandwidth L-band high electron mobility transistor (HEMT) amplifier are presented. No facilities-were available for measuring low-temperature S parameters, but the HEMT noise parameters were measured at a physical temperature of 12 K. The absence of S-parameter information precluded the design of a feedback amplifier, so a balanced configuration was adopted. This has the advantage of providing a good input match even though the amplifiers in the two arms of the balanced circuit are poorly matched. However, there are disadvantages. The loss of the input hybrid degrades the noise temperature and coupling errors in the hybrids, and differences between the amplifiers reduce the gain and result in a noise contribution from the input load. In the amplifier described, these effects degrade the noise temperature by less than 1 K. The amplifier uses commercially available packaged HEMT devices. At a physical temperature of 12 K the amplifier achieves noise temperatures between 3 and 6 K over the 1 to 2 GHz band. The associated gain is approximately 20 dB. >

A cooled 1-2 GHz balanced HEMT amplifier

The cryogenic noise temperature performances of a two-stage and a three-stage 32-GHz HEMT (high-electron-mobility transistor) amplifier were evaluated. The amplifiers utilize quarter-micrometer conventional AlGaAs/GaAs HEMT devices, hybrid matching input and output microstrip circuits, and a cryogenically stable DC biasing network. The noise temperature measurements were performed in the frequency range of 31 to 33 GHz over a physical temperature range of 300 to 12 K. Across the measurement band, the amplifiers displayed a broadband response, and the noise temperature was observed to decrease by a factor of ten in cooling from 300 to 15 K. The lowest noise temperature measured for the two-stage amplifier at 32 GHz was 35 K with an associated gain of 16.5 dB, while for the three-stage amplifier it was 39 K with an associated gain of 26 dB. It was further observed that both amplifiers were insensitive to light. >

32-GHz cryogenically cooled HEMT low-noise amplifiers

The cryogenic noise temperature performance of a two-stage and a three-stage 32 GHz High Electron Mobility Transistor (HEMT) amplifier was evaluated. The amplifiers employ 0.25 micrometer conventional AlGaAs/GaAs HEMT devices, hybrid matching input and output microstrip circuits, and a cryogenically stable dc biasing network. The noise temperature measurements were performed in the frequency range of 31 to 33 GHz over a physical temperature range of 300 K down to 12 K. Across the measurement band, the amplifiers displayed a broadband response, and the noise temperature was observed to decrease by a factor of 10 in cooling from 300 K to 15 K. The lowest noise temperature measured for the two-stage amplifier at 32 GHz was 35 K with an associated gain of 16.5 dB, while the three-stage amplifier measured 39 K with an associated gain of 26 dB. It was further observed that both amplifiers were insensitive to light.

G. G. Ortiz

Papers

32-GHz cryogenically cooled HEMT low-noise amplifiers

On 32-GHz cryogenically cooled HEMT low-noise amplifiers