摘要:

Recent experimental results on the photoluminescence and photoluminescence excitation of GaAs‐Ga0.51In0.49P lattice‐matched quantum wells and superlattices are discussed. The full width at half maximum of a 10‐period GaAs‐GaInP superlattice withLz=90 A˚ andLB=100 A˚ is 4 meV at 4 K. The photoluminescence excitation exhibits very sharp peaks attributed to the electron to light‐hole and electron to heavy‐hole transitions. The GaInP‐GaAs interface suffers from memory effect of In, rather than P or As elements.

ISSN:0003-6951    

DOI:10.1063/1.106336

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

High power cw operation of horizontal cavity monolithic GaAs/GaAlAs surface‐emitting lasers with all dry etched micromirrors in the junction‐up configuration has been demonstrated for the first time. The 45° and 90° mirrors of the devices were fabricated by ion beam etching and reactive ion etching techniques, respectively. Typical threshold current densities of less than 360 A/cm2, external differential efficiencies of 22% (0.34 W/A) from the emitting facet, and output powers in excess of 280 mW were achieved under cw operation.

ISSN:0003-6951    

DOI:10.1063/1.106337

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A significant reduction in lasing threshold is achieved by rapid thermal annealing (RTA) for strained InGaAs/GaAs single quantum well lasers grown by molecular beam epitaxy under standard conditions (the growth temperature is 620 °C or less), not especially optimized for lasers. When RTA at 900 °C for 10 s is applied twice to the wafer after the growth, the room‐temperature photoluminescence efficiency of the active layer increases by about 80 times and the threshold current decreases by a factor of 5 to 7. We suggest that this enhancement is due to improvement of the quality of the InGaAs quantum well rather than that of the AlGaAs cladding layers.

ISSN:0003-6951    

DOI:10.1063/1.106338

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Thin films ranging from 400 nm to 4 &mgr;m thickness of poly( p‐phenylene biphenyltetracarboximide) (BPDA‐PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by the optical waveguide spectroscopy. These polyimide films, most prominent for potential applications as the interlevel dielectrics in multilevel interconnect technologies owing to their low coefficients of thermal expansion and excellent thermal/mechanical properties, are found to exhibit an extraordinarily large anisotropy in the refractive index, with the measured in‐plane refractive indexn∥&bartil;1.852 and the out‐of‐plane valuen⊥&bartil;1.612 at 632.8 nm wavelength, nearly independent of the film thickness. This large optical anisotropy indicates a very strong preference of polymer chains to orient along the film surface, and suggests a considerably larger (by ca. 27%) dielectric constant in the film plane than that along the film thickness. Moreover, there is some evidence for the existence of a very thin polyimide layer of slightly lower density and higher anisotropy adjacent to the substrate.

ISSN:0003-6951    

DOI:10.1063/1.106339

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A novel edge‐emitting periodic index separate confinement heterostructure (PINSCH) semiconductor quantum well laser is proposed and demonstrated for the first time. Periodic semiconductor multilayers are used as optical confinement layers to simultaneously reduce the transverse beam divergence and increase the maximum output power. Self‐aligned ridge‐waveguide InGaAs/GaAs/AlGaAs PINSCH quantum well lasers emitting at 980 nm are fabricated. The 5×750 &mgr;m device has far‐field angles of 10° by 20°, a threshold current of 45 mA, an external differential quantum efficiency of 1.15 mW/mA (90%), and an output power exceeding 620 mW, all measured at room temperature under CW operation. A record high fiber coupling efficiency of 51% has been achieved with a lensed fiber of 5 &mgr;m core diameter.

ISSN:0003-6951    

DOI:10.1063/1.106340

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Symmetric self‐electro‐optic effect devices (S‐SEEDs) using extremely shallow GaAs/Al0.04Ga0.96As multiple quantum wells are demonstrated. By exploiting mainly exciton ionization, rather than the usual quantum‐confined Stark shift, room‐temperature optical bistability is obtained with no applied bias. The extremely shallow symmetric‐SEED (symmetric E‐SEED) exhibits contrast ratios (CRs)&bartil;3.5, with biasses<5 V, demonstrating system applicability and compatability with electronics. Large system tolerances &Dgr;&lgr;&bartil;6 nm and maximum bistability loop width &bartil;70% are also obtained. Moreover, due to fast carrier escape times, the symmetric E‐SEED exhibits useful CRs≳2 even at continuous‐wave intensities ≳70 &mgr;W/&mgr;m2.

ISSN:0003-6951    

DOI:10.1063/1.106341

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A Monte Carlo simulation of electron transport is used to predict the dependence of the ionization efficiency on the magnetic field strength of a planar magnetron. This offers insight into the operation of the magnetron, and it also provides two valuable practical results. First, the efficiency increases with field strength only up to a saturation level. Operating a magnetron with a stronger field strength would only lead to an undesirable loss of target utilization. Second, a scaling law is found that is useful for designing magnetrons of different sizes.  

ISSN:0003-6951    

DOI:10.1063/1.106342

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on Brillouin light scattering investigations on chemical‐vapor‐deposited polycrystalline diamond films. Besides the longitudinal and two transverse acoustic bulk phonons, a Rayleigh surface mode is observed. From the bulk modes the elastic constantsc11,c12, andc44of 1062±74, 122±8, and 541±22 GPa, respectively, are determined exhibiting the characteristic values of natural diamond. The observed Rayleigh mode sound velocity of 10326±470 m/s is consistent with the (110) texture of the polycrystalline film and the determined elastic constants.

ISSN:0003-6951    

DOI:10.1063/1.106343

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

GaN epilayers were grown on GaAs substrates by gas‐source molecular‐beam‐epitaxy technique using dimethylhydrazine as a nitrogen source. It was found that cubic GaN grows on GaAs (001) surfaces epitaxially, while hexagonal GaN grows on GaAs (111) surfaces, from the analyses of x‐ray diffraction and reflection high‐energy electron diffraction patterns. Cathodoluminescence measurements suggested that the band‐gap energy of cubic GaN is around 0.37 eV larger than that of hexagonal GaN.

ISSN:0003-6951    

DOI:10.1063/1.106344

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A straightforward kinematic analysis of diffraction from metastable three‐dimensional crystallites of Ge grown on Si(001) is presented. Low‐energy electron diffraction data from these crystallites agree with diffraction images calculated for a structure determined from scanning‐tunneling microscopy data. Additionally, reflection high‐energy electron diffraction images predicted for these crystals agree with existing data.

ISSN:0003-6951    

DOI:10.1063/1.106345

出版商:AIP    

年代:1991

数据来源: AIP