Perry A. Macdonald

Temperature dependence of DC and RF characteristics of AlInAs/GaInAs HBT's

Device characteristics of compositionally graded AlInAs/GaInAs heterojunction bipolar transistors (HBTs) measured and analyzed from cryogenic temperatures up to 250 degrees C are discussed. Excellent stability in DC and RF performance is observed at elevated temperatures, which is desirable for high-speed and high-density integrated circuit applications. DC current gain exhibits about 10% variation over the entire measured temperature range. F/sub T/ and f/sub max/ at 125 degrees C decreased by approximately 10% from their room-temperature values while improving steadily when the device was cooled down to near-liquid-helium temperature, the common-emitter breakdown voltage is 8.0 V at room temperature and reduces to 7.5 V at 125 degrees C. Likewise, the collector-base breakdown voltage and the base-emitter breakdown voltage reduce by about 0.5 V over the same temperature range. The breakdown voltages increase significantly at cryogenic temperatures. The low turn-on voltage and excellent low-temperature characteristics make the AlInAs/GaInAs HBT attractive for cryogenic applications. >

High performance microwave elements for SiGe MMICs

We demonstrate a low cost, manufacturable method for fabricating microwave elements on lossy substrates as required for Si-based devices. These microwave elements require a ground-plane on the surface of the Si substrate to shield the lossy dielectric below and use a 13 /spl mu/m thick layer of benzocyclobutene (BCB) for wave propagation. The performance of the transmission lines and MMICs thus fabricated are comparable to their GaAs counterparts.

Microwave power performance of InP-based double heterojunction bipolar transistors for C- and X-band applications

We report on the microwave performance of InP-based double heterojunction bipolar transistors (DHBT) for X-band and C-band applications with power cells operating at an output power greater than 2 W. Our power performance characterization indicated a combination of high power density and high efficiency at both 4.5 and 9 GHz. At 4.5 GHz we measured over 2 W output power (4.3 W/mm power density) and a peak power-added-efficiency (PAE) of 60%. AT 9 GHz the peak measured power was over 1 W (5 W/mm) and the peak PAE was 60%. These are the first reports of substantial microwave power performance in this new device technology based on the InP material system.<<ETX>>

Fabrication and characterization of high-T/sub c/ superconducting X-band resonators and bandpass filters

Microstrip passband filters with 3, 6, and 11 poles, as well as microstrip resonators, have been fabricated using postannealed Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub x/ (YBCO) films deposited on LaAlO/sub 3/ substrates using three-target simultaneous co-sputtering. The insertion loss in the passband for the filters with center frequencies between 9.5 and 13.4 GHz was <or=0.3 dB at 50 K and <or=0.6 dB at 77 K for the three- and six-pole filters, respectively. The out-of-band rejection was greater than 50 dB. The excellent filter performance was attributed to the use of highly c-axis oriented postannealed YBCO films. The quality of these films depended strongly on substrate preparation, film thickness, density of YBCO grain boundaries, and crystallographic orientation of the grains. Microstrip ring resonators fabricated with optimized YBCO films had Q values as large as 3800 at 9.5 GHz. The surface resistance and penetration depth for the YBCO films were determined from the temperature dependence of the measured Q values and resonant frequencies of the resonators.

Characterization of microstrip discontinuities on LaAlO/sub 3/

The difference between microstrip-coupled line filter designs using quasi-static and full-wave analyses on LaAlO/sub 3/ is discussed. Comparative data for CAD (computer-aided design) predictions and direct measurement for selected microstrip discontinuities on LaAlO/sub 3/ substrates are presented, as well as measured and predicted filter performance.<<ETX>>