摘要:

Wurtzite GaN was grown by gas source molecular beam epitaxy on (0001) sapphire substrates. Taking advantage of the catalytic decomposition of ammonia on the growing surface, high growth rates (>1 &mgr;m/h) were achieved for substrate temperatures ranging between 800 and 850 °C. Surface morphology, structural, and optical properties of thick (2–4 &mgr;m) GaN films were investigatedversusthe growth temperature of the GaN buffer layer. It is shown that this parameter has a drastic influence on the GaN properties. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119526

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The doping dependent intermixing of ZnCdSe/ZnSe superlattices was studied by secondary ion mass spectroscopy. The chlorine or nitrogen doped and undoped structures were grown by molecular beam epitaxy. Heat treatment was performed in the temperature range of 300 to 550 °C under different conditions, namely Zn or N atmosphere, vacuum and protected by aSi3N4cap. The diffusion of Cd was found to be Fickian for all kinds of doping. While identical Cd diffusion coefficients were observed for the undoped and the chlorine-doped superlattice, a distinct enhancement by three orders of magnitude was found for nitrogen-doped structures. Thep-type conductivity, and not the nitrogen itself, was identified to be responsible for the Cd diffusion enhancement by additional implantation studies. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119509

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated a particular class of photovoltaic quantum well intersubband photodetectors. Each period of the active region in these structures consists of four zones, namely an excitation zone, a drift zone, a capture zone, and a tunneling zone. The devices show pronounced photovoltaic behavior and high detectivities. In particular, the responsivity without external bias is substantially enhanced if resonant carrier capture is achieved due to an appropriate design of the capture zone. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119510

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The determination of the above band gap optical properties of zincblendeCd1−xMgxTe(0⩽x⩽0.5) ternary alloys are reported on. Using the parabolic-band critical point model, room-temperature critical point energies of theE0,E0+&Dgr;0,E1,E1+&Dgr;1,E2, andE0′interband transitions from numerically calculated second energy derivatives of ellipsometric spectra were obtained. The presence of two distinct structures in theE2feature forx>0was also observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119511

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Silicon nitride films are deposited onto monocrystallinep- andn-type silicon wafers by low-frequency plasma-enhanced chemical vapor deposition. Using small-pulse deep-level transient spectroscopy, three different types of defects are identified at the silicon–silicon nitride interface. All defects are located in the lower half of the silicon band gap and show a very broad Gaussian-like distribution of the state density. For all three defects, the capture cross sections for electrons,&sgr;n,and holes,&sgr;p,decrease strongly towards the conduction and valence band edge, respectively, while the capture cross-section ratio&sgr;n/&sgr;pat midgap, and hence the resulting recombination rate, is very different for each defect type. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119512

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have found that the extremely extended platelets of about 1 &mgr;m in diameter are formed in GaAs by He-ion implantation and subsequent annealing at 250 and 300 °C for the short period of 180–300 s. We have shown that the platelets are extended not on the most easily cleavaged {110}-type planes but on {111}-type planes. The platelets give rise to the extra transmission electron diffraction spots. The analysis of the diffraction, combined with electron microscopy data, has shown that unreconstructed interior {111} surfaces, oppositely bent, are created in GaAs. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119513

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Phononless radiative recombination is observed in luminescence spectra of Ge quantum wells decorated by self-organized Stranski–Krastanow (S–K) dots grown on Si (100). External uniaxial tensile stress along [011] allows the discrimination of phonon-missing optical transitions. The phononless recombination is attributed to a dipole-allowedkdiagonal&Dgr;1-&Ggr;25′interband transition involving the hole in the Ge wetting layer and the electron in a Siquantum dotencompassed by large S–K dots. The weak oscillator strength of the phononless recombination is evidenced by its slow decay kinetics. The results indicate that low-lying broad band features due to S–K dots are also of phononless origins. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119514

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Data are presented on the planar (top–down) oxidation of gradedAlxGa1−xAsupper confining layers of quantum well heterostructures in order to realize high resolution square-edge lasers (or waveguides). A model is developed to facilitate composition grading ofAlxGa1−xAsfor vertical-wall (square corner or edge) planar oxidation at convenient oxidation times and tolerances. A simple AlGaAs–GaAs quantum well laser structure is used to demonstrate the square-wall (square-corner) planar oxidation method. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119918

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

It has been established that the oxygen aggregation processes in Czochralski-grown silicon (Cz–Si) at 450 °C are strongly affected by high hydrostatic pressure. We observed the enhanced production of shallow thermal donors with ionization energies of 30–40 meV and deep donors at≈EC−0.1eV under a pressure of 1 GPa. In contrast, the concentration of the well-known double thermal donors was found to be much less than that in Cz–Si heat treated without stress. The latter effect may be associated with the involvement of self-interstitials in their formation. The enhanced production of other thermal donors is thought to be caused by increasing diffusivity of oxygen under the high stress. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119527

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Tungsten films, grown by plasma-enhanced chemical vapor deposition for very large scale integration interconnect applications, suffer from a high internal tensile stress that leads to contact failure. We show with wafer curvature measurements that the stress can be relaxed via viscous flow at room temperature by irradiating the films with energetic ions after deposition. Transmission electron microscopy does not indicate significant structural changes in the W films during irradiation. We varied the irradiation conditions (from 140 keV B ions to 400 keV P ions) and find that the flow rate scales with the nuclear stopping power. Similarities and differences with beam-induced mixing and diffusion are discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119515

出版商:AIP    

年代:1997

数据来源: AIP