摘要:

Molecular‐beam epitaxy was used to grow a 100 nm Al0.1Ga0.9N/100 nm GaN/500 nm Al0.1Ga0.9N double heterostructure on a 10‐&mgr;m‐thick GaN buffer layer grown with hydride vapor phase epitaxy on (0001) sapphire. Lasing from the 100 nm GaN active layer has been obtained at ∼359 nm at liquid‐nitrogen temperature (77 K) and at ∼365 nm at room temperature (295 K), using transverse optical pumping at 337.1 nm with a 600 ps transversely excited atmospheric pressure pulsed nitrogen laser. Threshold pump fluences were measured to be 0.3 and 0.5 mJ/cm2at 77 and 295 K, respectively, for a laser with 65 &mgr;m cavity length. In a laser of 23 &mgr;m cavity length, longitudinal cavity modes were observed with 0.56 nm spacing, corresponding to a group refractive index of 5.0 at the lasing wavelength. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361044

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Surface and interface properties of CdTe/CdS/SnO2/glass heterojunction solar cells are studied by means of x‐ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), and optical reflectance (OR) techniques. First,n‐type CdS layer was grown by solution growth technique on the SnO2coated glass substrate and then thep‐type CdTe was deposited on CdS by metal‐organic chemical‐vapor deposition. Despite many other efficiency limiting mechanisms in CdTe solar cells, this article shows that surfaces and interfaces play an important role in determining the cell efficiency. In an attempt to correlate the surface and interface properties to the cell performance, a series of CdTe/CdS solar cells with different conversion efficiencies were fabricated and analyzed. It was found that high efficiency cells possess Te‐rich CdTe surface along with smooth interfaces, as revealed by XPS, SIMS, and OR measurements, while low efficiency cells display near stoichiometric or Cd‐rich CdTe surface and abrupt interfaces. The impact and role of interface/surface properties on CdTe solar cell performance are discussed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361041

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A theoretical study of the magnetic‐field dependence of the two‐dimensional electron‐gas density, cyclotron mass, and Fermi energy in a modulation‐doped GaAs–Ga1−xAlxAs heterojunction under a magnetic field applied perpendicular to the interface is presented. The study, based on both the envelope‐function approximation and a parametric self‐consistent approach, takes into account band‐nonparabolicity effects. Numerical results show that the above‐mentioned quantities as well as a screening parameter introduced in the calculations are oscillatory functions of the magnetic field. Our results are in good agreement with experimental data previously reported and show that nonparabolicity may significantly influence the behavior of the cyclotron‐resonance parameters. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361079

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The theoretical study on the differential gain of InxGa1−xAs/InGaAsP quantum‐well (QW) lasers lattice matched to GaAs is presented. These results were also compared with those of InxGa1−xAs/GaAs QW lasers. The differential gain of InGaAs/InGaAsP lasers continuously increases with the In composition. On the other hand, InGaAs/GaAs lasers show the decrease of the differential gain when the In composition exceeds about 0.22. The increase of the differential gain observed in InGaAs/InGaAsP lasers is mainly due to the increase of the subband energy spacing in the conduction band. The decrease of the differential gain observed in InGaAs/GaAs lasers is related to the decrease of the energy spacing in the conduction band and the decrease of the optical matrix element. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361042

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

During the first thermal treatment after deposition and/or passivation of Al‐based interconnects, a marked decrease in the electrical resistance can be observed. This resistance decrease cannot be described in terms of a single rate constant. Precipitation of the alloyed elements is probably the responsible atomic process. In a previous article, a spectrum of activation energies was extracted in order to characterize this decay. Recent research has shown that the presence of an activation energy spectrum is, mathematically, completely equivalent with a spectrum of pre‐exponential factors. Since for precipitation–dissolution, the pre‐exponential factor is a function of the distribution and geometry of the precipitates, the use of a spectrum of pre‐exponential factors is for this specific case probably physically more relevant. The technique introduced for the determination of the spectrum of activation energies is still valid in case of the presence of a spectrum of pre‐exponential factors. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362338

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose a method to determine the band offset of a heterojunction based on the elimination of the diffusion potential. In0.5Ga0.5P/GaAs heterojunction samples were used for demonstration of this method. As many error sources related to the determination of diffusion potential are avoided in our case, the more accurate value of 137±5 meV has been obtained for the conduction‐band discontinuity. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361077

出版商:AIP    

年代:1996

数据来源: AIP