R.A. Metzger

39.5-GHz static frequency divider implemented in AlInAs/GaInAs HBT technology

A static divide-by-four frequency divider operating at 39.5-GHz input frequency is reported. Graded emitter-base junction AlInAs/GaInAs heterojunction bipolar transistor (HBT) technology lattice-matched to InP substrates has been used to implement the divider. The graded junction HBTs feature unity gain cutoff frequency and maximum frequency of oscillation of 130 GHz and 91 GHz, respectively. The devices have a very low turn-on voltage of about 0.7 V at collector current density of 5*10/sup 4/ A/cm/sup 2/. The divider operated at a power supply voltage of -3 V and consumes a total DC power of 425 mW, corresponding to 77 mW per flip-flop.<<ETX>>

A deep-submicrometer microwave/digital CMOS/SOS technology

0.35- mu m complementary metal-oxide-semiconductor (CMOS)/silicon-on-sapphire (SOS) n- and p-channel MOSFETs with a metal-over-polysilicon T-gate structure for monolithic microwave integrated circuit (MMIC) and digital applications are reported. The measured values for the current-gain cutoff frequency f/sub T/ were >or=20 GHz for both n-channel and p-channel devices, and the values for the unilateral power-gain cutoff frequency f/sub max/ were 37 GHz for the p-channel and 53 GHz for the n-channel MOSFETs. The low effective resistance of the T-gate structure contributed to the very high f/sub max/ values. It is believed that these are the highest f/sub T/ and f/sub max/ values ever reported for MOS devices. The potential of SOS submicrometer MOSFETs for microwave circuit applications is demonstrated.<<ETX>>

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. >

The effects of base dopant diffusion on DC and RF characteristics of InGaAs/InAlAs heterojunction bipolar transistors

The effects of base p-dopant diffusion at junction interfaces of InGaAs/InAlAs HBTs with thin base thicknesses and high base dopings are reported. It is shown that HBTs with compositionally graded emitter-based (E-B) junctions are very tolerant to base dopant outdiffusion into the E-B graded region. The RF performance is nearly unaffected by the diffusion, and the DC current gain and E-B junction breakdown voltages are improved with finite Be diffusion into the E-B graded region.<<ETX>>

Growth and characterization of low temperature AlInAs

Abstract Al0.48In0.52As lattice matched to InP and grown by MBE over a temperature range of 250 to 100°C and under an As4 pressure of 1x10−6 to 2x10−5 Torr has been investigated. Over this temperature range of 250 to 100°C, resistivity decreases from 2x107 to 3x106 Ω cm while photoluminescence intensity decreases by two orders of magnitude. Resistivity showed little sensitivity to change in As4 overpressure over the range investigated. Single crystal samples grown in the range of 100 to 150°C showed nonstochiometric excess As of up to 1.4% as determined by secondary ion mass spectrometry, and lattice expansion of 0.1% as determined by X-ray diffraction. Samples grown at temperatures greater than 200°C showed no excess As or lattice expansion.

Effect of Si movement on the electrical properties of inverted AlInAs–GaInAs modulation doped structures

Inverted modulation doped structures typically exhibit degraded electrical characteristics. For the AlInAs‐GaInAs heterojunction system, the reduction in electron mobility for two‐dimensional electron gases formed at inverted interfaces can be greater than 50% at 300 K as compared to those formed at normal interfaces. Our data show that the reduction in mobility is due to the movement of Si into the GaInAs channel. The Si movement is found to be dramatically reduced by growing the AlInAs spacer at the inverted interface at a substrate temperature of 300–350 °C. Device structures have been grown using this technique which exhibit the highest conductivity obtained for any 2DEG system.

33-GHz monolithic cascode AlInAs/GaInAs heterojunction bipolar transistor feedback amplifier

Microwave cascode feedback amplifiers with 8.6-dB gain and DC to 33-GHz bandwidth were developed. The amplifiers utilize AlIn-As/GaInAs heterojunction bipolar transistors having f/sub max/=70 GHz and f/sub tau /=90 GHz. Because of the significant collector-base feedback time constant the cascode configuration provides a large improvement in amplifier bandwidth, but a low-impedance bias node must be provided for the common-base transistor. An active bias network was thus used which eliminates the need for on-wafer Si/sub 3/N/sub 4/ bypass capacitors. >

Stability of beryllium‐doped compositionally graded and abrupt AlInAs/GaInAs heterojunction bipolar transistors

Stability of base‐emitter (BE) junction characteristics and dc current gain is analyzed for high‐performance AlInAs/GaInAs heterojunction bipolar transistors (HBTs). HBT devices with heavily beryllium‐doped base layers were stressed with a constant collector current at elevated temperatures (180 and 208 °C). Devices with compositionally abrupt and graded BE junctions were compared. The compositionally abrupt devices showed signs of significant Be diffusion under bias stress (i.e., drift in turn‐on voltage and drop in dc current gain). The graded junction devices, however, remained extremely stable under bias stress. The compositional grading at the BE junction was accomplished by a nine‐period AlInAs/GaInAs superlattice and is believed to be responsible for the stability of the graded devices.

Confinement of high Be doping levels in AlInAs/GaInAs npn heterojunction bipolar transistors by low temperature molecular‐beam epitaxial growth

AlInAs/GaInAs npn heterojunction bipolar transistors (HBTs) have been grown over a substrate temperature range of 280–450 °C with Be base doping levels ranging from 2.0×1019 to 1.6×1020 cm−3. We have determined that for a desired base doping level there exists an optimum growth temperature at which the Be is confined in the base and at the same time the dc current gain of the HBT is maximized.