摘要:

The effects of regions made semi‐insulating by ion implantation on the base current of a GaAs/AlGaAs heterojunction bipolar transistor (HBT) have been investigated. The implanted region, which overlaps both ends of the emitter and base fingers in the device structures studied, is intended to reduce parasitic capacitances. It is shown that the current between the base and emitter fingers at these implant isolation edges can be divided into two distinct components: a leakage current which is linear with bias and a recombination current which has an ideality of 2.0. Both of these parasitic current components reduce the HBT current gain, particularly at low current densities. A measurement technique was developed to separate these two currents using dc current‐voltage characteristics of the device.

ISSN:0021-8979    

DOI:10.1063/1.351942

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A nonisothermal drift‐diffusion model of avalanche diodes is described. The novel feature of the model is the inclusion of the heat conduction equation in the basic set of semiconductor equations. The influence of a nonuniform temperature distribution across the active region on the diode electrical characteristics is investigated and the usual assumption of constant diode junction temperature is evaluated. Both single‐drift and double‐drift diodes are simulated. The temperature distribution is calculated as a function of the dc bias current density and the amplitude of the rf driving voltage. The diode impedance is also determined and compared with results from an isothermal simulation. Numerical results are presented atJ‐(10–20 GHz) andW‐band frequencies (75–110 GHz).

ISSN:0021-8979    

DOI:10.1063/1.351943

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report on a picosecond YBa2Cu3O7−&dgr;detector for far‐infrared radiation. The detector, consisting of a current carrying structure cooled to liquid‐nitrogen temperature, was studied by use of ultrashort laser pulses from an optically pumped far‐infrared laser in the frequency range from 25 to 215 cm−1. We found that the sensitivity (1 mV/W) was almost constant in this frequency range. We estimated a noise equivalent power of less than 5×10−7W Hz−1/2. Taking into account the results of a mixing experiment (in the frequency range from 4 to 30 cm−1) we suggest that the response time of the detector was few picoseconds.

ISSN:0021-8979    

DOI:10.1063/1.351944

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new model has been developed to describe the &agr;‐quartz to stishovite phase transition in silica under shock‐loading conditions. During hydrodynamic simulations, individual global equations of state for the &agr;‐quartz and stishovite phases of silica are mixed in accordance with process‐dependent constraints on the Gibbs free energy difference between the phases (&Dgr;G). For the shock‐induced transition, &Dgr;Gis required to equal a simple two parameter function of the mass fraction of stishovite. Unlike previous models, the new constraint equation assumes that the shock induced phase transition begins at the equilibrium phase boundary, but is not completed unless peak stresses on the order of 40 GPa are achieved. On release, the reverse transition is required to satisfy the usual thermodynamic equilibrium condition (&Dgr;G=0). It is shown that hydrodynamic simulations combining this hysteretic phase transition model with a strength model that assumes partial softening after yielding are capable of reproducing experimental Hugoniot and release data for crystalline silica in the mixed‐phase region.

ISSN:0021-8979    

DOI:10.1063/1.351945

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A simple expression, obtained from the rate equation for defect production, was used to relate carrier removal to defect production and hole trapping rates inp‐type InP after irradiation by 1‐MeV electrons. Specific contributions to carrier removal from defect levels H3, H4, and H5 were determined from combined deep‐level transient spectroscopy (DLTS) and measured carrier concentrations. An additional contribution was attributed to one or more defects not observed by the present DLTS measurements. The high trapping rate observed for H5 suggests that this defect, if present in relatively high concentration, could be dominant inp‐type InP.

ISSN:0021-8979    

DOI:10.1063/1.351946

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Capacitance versus voltage curves and deep‐level transient spectroscopy have been used to investigate the effects of BCl3magnetron ion etching on the shallow donor concentration and deep‐level defects in GaAs. Capacitance versus voltage data reveal that the shallow donor concentration is unaffected by the etching process at power densities ranging from 0.08 to 0.4 W/cm2. Capacitance transient measurements reveal thermal emission of electrons from two deep defect sites with activation energies of 0.25 and 0.74 eV which were unaffected by the etching process. A broad, deep‐level transient spectroscopy peak, characterized by an activation energy for thermal emission of electrons of 0.37 eV, was also observed in the etched sample, but not in the unetched sample. Defect depth profiling of the 0.37 eV peak indicates the concentration of this defect to increase with increasing etch power.

ISSN:0021-8979    

DOI:10.1063/1.351947

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Bistability and switching are observed in the light versus current (L‐I) characteristic of a native‐oxide‐defined AlxGa1−xAs‐GaAs quantum‐well‐heterostructure stripe laser side‐coupled to a linear array of end‐coupled rectangular minilasers. These diodes, with internally coupled elements and the current partitioned among the elements, exhibit a large hysteresis in theL‐Icurve, with switching from the stimulated to the spontaneous regime occurring over substantial power (light) and current ranges. The linear array of minilasers and their resonances modulates and switches the stripe laser operation. The overall planar twin‐stripe laser structure is defined by H2O vapor oxidation (425 °C), in patterned form, of a significant thickness of the high‐gap AlxGa1−xAs upper confining layer of an AlxGa1−xAs‐GaAs quantum‐well heterostructure.

ISSN:0021-8979    

DOI:10.1063/1.351948

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Polycrystalline Bi4Ti3O12thin films having perovskite structure were successfully produced on platinum coated silicon substrates by the sol‐gel technique. Crack‐free and crystalline films of 5000 A˚ thickness were fabricated by spinning and post‐deposition rapid thermal annealing treatment at 500 °C for 20 s. The films exhibited good structural, dielectric, and ferroelectric properties. The measured dielectric constant and loss factor at a frequency of 100 kHz were 180 and 0.014 and remanent polarization and coercive field were 5.4 &mgr;C/cm2and 135 kV/cm, respectively. The films showed good switching endurance under bipolar stressing at least up to 1010cycles.

ISSN:0021-8979    

DOI:10.1063/1.351949

出版商:AIP    

年代:1992

数据来源: AIP