F. Williams

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. >

Reliability of AlInAs/GaInAs heterojunction bipolar transistors

The reliability of high-performance AlInAs/GaInAs heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy (MBE) is discussed. Devices with a base Be doping level of 5*10/sup 19/ cm/sup -3/ and a base thickness of approximately 50 nm displayed no sign of Be diffusion under applied bias. Excellent stability in DC current gain, device turn-on voltage, and base-emitter junction characteristics was observed. Accelerated life-test experiments were performed under an applied constant collector current density of 7*10/sup 4/ A/cm/sup 2/ at ambient temperatures of 193, 208, and 328 degrees C. Junction temperature and device thermal resistance were determined experimentally. Degradation of the base-collector junction was used as failure criterion to project a mean time to failure in excess of 10/sup 7/ h at 125 degrees C junction temperature with an associated activation energy of 1.92 eV. >

Reliability and failure criteria for AlInAs/GaInAs/InP HBTs

We have performed accelerated temperature and bias lifetests on single-heterojunction AlInAs/GaInAs/InP bipolar transistors (HBTs). Discrete HBTs were fabricated and stressed at bias conditions of high collector-emitter voltage, typical operating current (V/sub CE/=3 V and J/sub C/=23 kA/cm/sup 2/), and at junction temperatures (T/sub j/) of 205/spl deg/C and 225/spl deg/C. Previous lifetests had been presented at higher junction temperatures (T/sub j/>230/spl deg/C) and up to 2000 hours of stress. In this work, we report results from stress tests up to 6000 hours. Failure criteria defined by base-emitter turn-on voltage (V/sub BE/) and dc-gain (/spl beta/) degradation demonstrate a robust technology with activation energies (E/sub a/) greater than 1.1 eV and extracted median-time-to-failure (MTTF) in excess of 10/sup 7/ hours at T/sub j/=100/spl deg/C.

Reliability of InP-based HBT IC technology for high-speed, low-power applications

We report on the reliability of an InP-based heterojunction bipolar transistor IC technology for very high-speed and low power applications. We have performed extensive accelerated lifetest experiments under bias and temperature stress and found mean-time-to-failures (MTTF) in excess of 10/sup 7/ hours at 125/spl deg/C junction temperatures. We have also exposed our devices to a hydrogen ambient, particularly important for integrated circuits in hermetically sealed packages. We did not observe any difference in the characteristics of devices with or without exposure to hydrogen ambient. In addition we have performed extensive lifetest experiments on tantalum-nitride (TaN) thin-film resistors (TFR) used in our IC process. Our TFR reliability performance exceeded the active device reliability, as required in a reliable IC process.<<ETX>>

Monolithic fabrication of NPN and PNP AlInAs/GaInAs HBTs

The authors demonstrated the feasibility of a new technique for the monolithic fabrication of complementary heterostructure bipolar transistors (HBTs). The process led to coplanar npn and pnp HBTs, the first in the AlInAs/GaInAs material system, which were comparable with the state of the art in HBTs. These devices exhibited unity current gain cutoff frequencies (f/sub T/) up to 99 GHz and 14 GHz for the npn and pnp transistors, respectively. The fabrication scheme allows each of these device types to have individually designed epitaxial structures that are grown in a single molecular beam epitaxy run. Results show that the devices will be capable of tight packing densities for IC applications.<<ETX>>

Power performance and reliability of AlInAs/GaInAs/InP double heterojunction bipolar transistors

AlInAs/GaInAs/InP double heterojunction bipolar transistors (DHBT) combine the high-frequency performance advantages of the InP-based HBT technology with the high breakdown and low output conductance advantages of the GaAs-based HBTs. InP-based DHBTs reported here are composed of a wide bandgap AlInAs emitter, a GaInAs base, and a wide bandgap InP collector. The two heterojunctions are compositionally graded to smooth out the potential barriers at the heterointerfaces. We have used physical device modeling to analyze the device performance, particularly at high current densities. DHBTs have high Early voltages and are therefore suitable for analog circuit applications. In this paper we concentrate on the high breakdown property of this device technology for microwave power amplification. We have fabricated and characterized power cells with 240 /spl mu/m/sup 2/ emitter geometries. We measured power densities as high as 6 W/mm/sup 2/ on power cells biased at 11 V and power added efficiencies of 60% on power cells biased at 10 V for applications at X-band frequencies. For integrated circuit applications, DHBTs which are epitaxially grown with a gas-source MBE system exhibit stable current gain and turn-on voltage characteristics under bias and temperature stress.<<ETX>>

Performance of AlInAs/GaInAs/InP microwave DHBTs

The authors report the experimental characteristics obtained from AlInAs/GaInAs/InP double heterojunction bipolar transistors (DHBTs) grown by gas source molecular beam epitaxy. They describe the fabrication and measured performance of two AlInAs/GaInAs/InP DHBT structures, one having a relatively thin 390 nm collector and the other having a relatively thick 1200 nm collector. Their performance results are presented within the context of their application to linear ICs and microwave power amplification. The results include the first reported microwave power measurements on this InP-based DHBT structure featuring a continuous wave output power density of 3.3 W/mm at 4 GHz.<<ETX>>

HTS microstrip matching networks and filters

High-temperature superconducting (HTS) YBCO microstrip bandpass filters and microstrip impedance matching networks were fabricated, tested and compared with the predicted performance. Vector corrected measurements of these circuits were performed at cryogenic temperatures. Comparisons of the insertion loss for the HTS and corresponding Au filters are presented, as well as the predicted noise figure for the low-noise amplifiers using HTS and Au matching networks. >

Multigigahertz monolithic GaAs optoelectronic receivers using 0.2 mu m gate-length MESFETs

Two GaAs optical receiver front-ends are reported. Each consists of an MSM photodetector and a transresistance amplifier that drives a 50 Omega load. One amplifier has a measured analog bandwidth of 6.5 GHz, while the other has one of 4.5 GHz. The transresistance-bandwidth product for both is 2.1 THz- Omega .<<ETX>>

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>>