An analytical formula is derived to calculate the inductance of a finite-width superconducting strip transmission line. The formula gives an accurate inductance value when the aspect ratio (the ratio of the linewidth to the insulation thickness) exceeds about unity.

A graded-composition electron blocking layer (GEBL) with aluminum composition increasing along the [0001] direction was designed for c-plane InGaN/GaN light-emitting diodes (LEDs) by employing the band-engineering. The simulation results demonstrated that such GEBL can effectively enhance the capability of hole transportation across the EBL as well as the electron confinement. Consequently, the LED with GEBL grown by metal-organic chemical vapor deposition exhibited lower forward voltage and series resistance and much higher output power at high current density as compared to conventional LED. Meanwhile, the efficiency droop was reduced from 34% in conventional LED to only 4% from the maximum value at low injection current to 200 A/cm2.

Material properties and performance of metamorphic optoelectronic integrated circuits grown by molecular beam epitaxy on GaAs substratesA technique for the heteroepitaxy of GaAs/Si films having reduced threading dislocation density is presented. The important attribute of this technique is the suppression of three-dimensional Volmer-Weber island formation during initial deposition. This suppression is achieved by deposition of a stoichiometric GaAs buffer layer by a migration-enhanced epitaxy technique on silicon at 348 K to a thickness greater than the ''monolithic thickness,'' h m . Subsequent GaAs films deposited by conventional molecular beam epitaxy on buffer layers of thickness greater than h m possess structural and optical characteristics that exceed those for state-of-the-art GaAs/Si layers: an x-ray full width at half maximum ͑FWHM͒ of 110 arcsec with a dislocation density at the film surface of 3ϫ10 6 cm Ϫ2 and a concomitant 4 K photoluminescence FWHM of 2.1 meV. The p-i-n structures suitable for use as light-emitting diodes ͑LEDs͒ that were grown on the reduced threading dislocation density GaAs/Si and by means of forward-and reverse-bias measurements, demonstrated an ideality factor of nϭ1.5, an increased reverse-bias breakdown electric field of 2.1ϫ10 7 V/m, and an intrinsic region resistivity of 4ϫ10 7 ⍀ cm for LEDs of increasingly smaller mesa size.

InGaN/GaN light-emitting diodes ͑LEDs͒ with graded-thickness multiple quantum wells ͑GQW͒ was designed and grown by metal-organic chemical vapor deposition. The GQW structure, in which the well-thickness increases along ͓0001͔ direction, was found to have superior hole distribution as well as radiative recombination distribution by performing simulation modeling. Accordingly, the experimental investigation of electroluminescence spectrum reveals additional emission from the narrower wells within GQWs. Consequently, the efficiency droop can be alleviated to be about 16% from maximum at current density of 30 to 200 A / cm 2 , which is much smaller than that for conventional LED ͑32%͒. Moreover, the light output power was enhanced from 18.0 to 24.3 mW at 20 A / cm 2 .

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