Secondary ion mass spectrometry (SIMS) provides direct methods to characterize the chemical composition of III-V materials at major, minor and trace level concentrations as a function of layer depth. SIMS employs keV primary ions to sputter the surface and sensitive mass spectrometry techniques to mass analyze and detect sputtered secondary ions which are characteristic of the sample composition. In-depth compositional analysis of these materials by SIMS relies on a number of its unique features including: (1) keV primary ion sputtering yielding nanometer depth resolutions, (2) the use of MCs+ detection techniques for quantifying major and minor constituents, and (3) ion implant standards for quantifying trace constituents like dopants and impurities. Nanometer depth resolution in SIMS sputtering provides accurate detection of diffusion of dopants, impurities and major constituents. MCs+ refers to the detection of “molecular” ions of an element (M) and the Cs+ primary beam. MCs+ minimizes SIMS matrix effects in analysis for major and minor constituents, thus providing good quantification. This paper presents a SIMS study of AlxGa1−xAs structures with three different x values. MCs+ (M=Al or Ga) data are presented for the accurate determination of major and minor components. Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD) data were crosscorrelated with the MCs+ results. Three specimens with different x values were ion implanted with H, C, O, Mg, Si, Zn and Se to study quantification of trace levels. SIMS data acquired on a double focusing instrument (CAMECA IMS-4f) and a quadrupole instrument (PHI ADEPT 1010) are also compared. Lastly, we discuss our efforts to improve the analysis precision for pand n-type dopants in AlGaAs which currently is ± 3% (1 sigma).

A hybrid double heterostructure with large asymmetric band offsets, combining AlAsSb/InAs (as a III–V part) and CdMgSe/CdSe (as a II–VI part), has been proposed as a basic element of a mid-infrared laser structure design. The p-i-n diode structure has been successfully grown by molecular beam epitaxy (MBE) and exhibited an intense long-wavelength electroluminescence at 3.12 μm (300K). A II–VI MBE growth initiation with a thin ZnTe buffer layer prior to the CdMgSe deposition results in a dramatic reduction of defect density originating at the II–VI/III–V interface, as demonstrated by transmission electron microscopy. A less than 10 times reduction of electroluminescence intensity from 77 to 300K indicates an efficient carrier confinement in the InAs active layer due to high potential barriers in conduction and valence bands, estimated as ΔEC = 1.28 eV and ΔEV ∼ 1.6 eV. An increase in the pumping current results in a super-linear raising the EL intensity. The type of band line up at the coherent InAs/Cd1−xMgxSe interface is discussed for 0≤x≤0.2, using experimental data and theoretical estimations within a model-solid theory.

The luminescence properties of erbium oxide grown on crystalline and amorphous silicon substrates were studied by means of photo- and cathodoluminescence techniques. Differences in the luminescence spectra for samples grown on the two types of substrates used are explained in terms of the different types of erbium centers formed by taking into account the substrate properties and the thermal treatments during growth. For comparison, erbium implanted and oxygen coimplanted crystalline and amorphous silicon have been also investigated by luminescence techniques. In the implanted samples, the sharp transitions from erbium ions in the visible range were quenched and the main emission corresponds to the intraionic transitions in Er3+ ions in the infrared range peaked at 1,54 μm.

This paper presents for the first time photo-assisted Metalorganic vapor phase epitaxial (MOVPE) growth of ZnMgS on Si (100) substrates. The growth was done using dimethylzinc (DMZn), bismethylcyclo-pentadienyl-magnesium ((MeCP)2Mg), and diethylsulfhide (DES) as zinc, magnesium, and sulfur precursors. Epitaxial characterization by X-ray Photoelectron Spectroscopy (XPS), and low - angle X-ray Diffraction (XRD) results are presented. Mg solid phase incorporation is estimated to vary from 0 to 60 percent. The epitaxial nature of the ZnMgS layers has been verified using the low-angle X-ray diffraction eliminating any interference from the Si substrate. It can be shown with this technique that the change in the ZnMgS peak position changes from 27.35 degrees to 26.5 degrees with an increase in Mg incorporation, compared with a Si control sample peak at 27.4 degrees. XRD results obtained have been verified with XPS data. Chlorine doping of the ZnMgS layer was also studied. Concentrations up to 3 × 1015 cm−3 were observed in the ZnMgS layer. Results of the n (ZnMgS:Cl) – p (Si) diodes fabricated are also presented.

Preparation of CdS nanoparticles, devices fabrication, and electroluminescence properties at room temperature of CdS nanoparticles on silicon substrates are reported. A spectral shift of 86-meV of free exciton transition was observed that was due to the passivation of p-hydroxyl thiophenol molecules around nanoparticles. Controlled process conditions such as heat treatment and/or with oxygen-rich environment are experimented and found to have significant influences on emission spectra. Radiative recombination corresponding to oxygen-impurity level, 273 meV below bandgap energy, presents in samples prepared in oxygen-rich environment. In addition to such mechanism, coalescence of nanoparticles into bulk form also exists and contributes to enhanced luminescence.

Highly sensitive optically detected resonance experiments have shown that magnetoexcitons in GaAs-(Ga,Al)As semiconductor quantum wells have discrete internal energy levels, with transition energies found in the far-infrared (terahertz) region. Here we are concerned with a theoretical study of the terahertz transitions of light-hole and heavy-hole confined magnetoexcitons in GaAs-(Ga,Al)As quantum wells, under a magnetic field applied in the growth direction of the semiconductor heterostructure. The various magnetoexciton states are obtained in the effective-mass approximation by expanding the corresponding exciton-envelope wave functions in terms of appropriate Gaussian functions. The electron and hole cyclotron resonances and intra-magnetoexciton transitions are theoretically studied by exciting the allowed electron, hole and internal magnetoexcitonic transitions with far-infrared radiation. Theoretical results are obtained for both the intra-magnetoexciton transition energies and oscillator strengths associated with excitations from 1s - like to 2s, 2p±, and 3p±- like magnetoexciton states, and from 2p- to 2s – like exciton states. Present results are in overall agreement with available optically detected resonance measurements and clarifies a number of queries in previous theoretical work.

Melting and crystallization experiments of InGaSb were done under the reduced gravity condition (10–2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.

The kinetics of the wet oxidation process of MBE-grown high-Al-content AlAs/Al0.6Ga0.4As short-period superlattices (SPSLs) was investigated and compared to AlGaAs alloys and pure AlAs. We found that alloys and superlattices (SLs) have different oxidation characteristics. These differences were attributed to traces of the superlattice structure in the oxidized material. The microstructure and chemistry of SPSLs with an equivalent composition of Al0.98Ga0.02As was studied, using transmission electron microscopy, energy-dispersive x-ray spectroscopy, Rutherford backscattering, and nuclear reaction analysis for hydrogen-profiling. We also report on the mechanical stability of oxidized SPSL layers in optoelectronic device structures.

GaN and its related alloys are being widely developed for blue-ultraviolet emitting and detection devices as well as high temperature, high power, and high frequency electronics. Despite the fast improvement in the growth of good quality GaN, a high concentration of deep level defects of yet unconfirmed origins are still found in GaN. For both optical and electronic devices, these deep carrier traps and/or recombination centers are very important and must therefore be understood. In the present work, deep level defects in GaN grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been investigated using Isothermal Capacitance Transient Spectroscopy (ICTS) and Current Voltage Temperature (IVT) measurements. Several deep level electron traps were characterized, obtaining the emission energy, concentration, and capture cross section from a fit of exponentials to the capacitance transients. ICTS was also used to reveal information about the capture kinetics involved in the traps found in GaN by measuring the amplitude of the capacitance transient at each temperature. At a reduced filling pulse where the traps were not saturated, several of them showed marked reduction in capacitance transient amplitude when compared to the transient amplitude measured under conditions where the filling pulse saturates the traps. This reduction in transient amplitude indicates that there is a barrier to carrier capture, in addition to the emission barrier. It has been found that several traps had capture barriers that were significant fractions of the emission energies up to 0.32 eV. These capture barriers may lead to persistent photoconductivity and reduced trapping. In this paper, deep level emission energies as well as capture barrier energies found in MOCVD-grown GAN will be discussed.

Ion implantation induced intermixing of GaAs/AlGaAs and InGaAs/AlGaAs quantum wells was studied using low temperature photoluminescence. Large energy shifts were observed with proton implantation and subsequent rapid thermal annealing. Energy shifts were found to be linear as a function of dose for doses as high as ∼5×1016 cm−2. Proton implantation and subsequent rapid thermal annealing was used to tune the emission wavelength of InGaAs quantum well lasers as well as detection wavelength of GaAs/AlGaAs quantum well infrared photodetectors (QWIPs). Emission wavelength of lasers showed blue shift whereas detection wavelength of QWIPs was red shifted with intermixing.

X-ray structural analysis, nuclear magnetic resonance, optical spectroscopy and second harmonic generation were used to characterize the new nonlinear crystals LiInS2 and LiInSe2 which possess maximum band gap (3.59 and 2.86 eV at 300 K, respectively) among ternary chalcogenides. As grown crystals are only slightly colored while color change after annealing is due to native point defects.

We have fabricated submonolayer-thick films of CdSe colloidal nanodots in order to investigate electronic properties of individual nanodots by conductive-tip atomic force microscopy (AFM). Topographic and current images of isolated single CdSe colloidal dots on single crystalline Au (111) surface which was covered with dodecanethiol self-assembled monolayer were obtained by AFM operating in contact mode with a conductive tip under appropriate bias voltages. In the current image, it is found that the dot regions have higher electric resistances due to tunneling resistance through the CdSe dots. We also found 10 nm-scale electric inhomogeneity around the dots, which may corresponds to the previously reported etch-pits of Au (111) surfaces formed during the deposition of the dodecanethiol molecules.

Simultaneous wet-thermal oxidation of MBE and MOCVD grown AlxGa1−xAs layers (× = 0.1 to 1.0) showed that the epitaxial growth method does not influence the oxidation rate. Nearly identical oxidation depths were measured for samples grown by both techniques. It was found, however, that the oxidation rate is very sensitive to non-uniformities in the Al concentration in the AlxGa1−xAs layers, and that maintaining consistent and uniform Al concentrations is critical to achieving reproducible oxidation rates. The study also showed that the oxidation rate was not affected by the V/III ratio during growth nor by impurities at concentrations less than or equal to 10 ppm.

In this paper, CVD diamond thin films for alpha particle detector have been prepared using hot-filament chemical vapor deposition (HFCVD) technique. Alpha particle detectors with coplanar and sandwich electrode geometry have been fabricated on the diamond films using liftoff technology. The detector performance has been tested using a 241 Am source with a characteristic energy of 5.5 MeV. An average charge collection efficiency of 32 % for the detector with coplanar and of 21 % for the detector with sandwich geometry is obtained.

A strong electron-phonon interaction observed in semiconductors allows to realize a special kind of atomic rebuilding under photo-irradiation of the medium. We consider three types of defective structures: one atomic, two-atomic (“dump-bell”) and multi-atomic (kinks) defects. It is shown that an inversion effect of the defect potential term may be realized if there are non-equivalent neighboring positions of one-atomic and two-atomic defects. In this case the photo-excitation of electronic subsystems of these defects leads to an inversion of potential terms and a consecutive athermal rebuilding of the defective structures. The Yahn-Teller effect and psevdo-effect play a special role here. It is shown for kink-structures that the photo-excitation of the electronic subsystems results in the alteration of kink nonius and the successive exponentially strong decrease of an activation barrier. Especially effects of athermal atomic rebuilding of U-negative defects are considerable.

It has been reported that Zn atoms diffused from the Zn-doped p-InAlP cladding to the active layer in InGaAlP visible-light-emitting diodes cause a degradation of light output efficiency. A doping effect of the Zn atoms was then investigated using a Piezoelectric Photothermal Spectroscopy from a nonradiative transition point of view. The results indicate that the Zn-doping unexpectedly induces a decrease of the nonradiative component of the electron transitions above the band gap of the active layer. The experimental results are explained by considering that Zn doping cause the increase of both shallow and deep acceptor levels at the same time with the different rate for generation.

In this paper we review recent progress achieved in our development of type-I GaInAsSb/AlGaAsSb quantum-well (QW) lasers with emission wavelength in the 1.74–2.34 μm range. Triple-QW (3-QW) and single-QW (SQW) diode lasers having broadened waveguide design emitting around 2.26 μm have been studied in particular. Comparing the two designs we have find that the threshold current density at infinite cavity length as well as the transparency current density scale with the number of QWs. Maximum cw operating temperature exceeding 50°C and 90°C has been obtained for ridge waveguide lasers emitting above and below 2 μm, respectively. Ridge waveguide diode lasers emitting at 1.94 μm exhibited internal quantum efficiencies in excess of 77%, internal losses of 6 cm−1, and threshold current density at infinite cavity length as low as 121 A/cm2 reflecting the superior quality of our diode lasers, all values recorded at 280 K. A high characteristic temperature TOof 179 K for the threshold current along with a value of T1 = 433 K for the characteristic temperature of the external efficiency have been attained for the 240–280 K temperature interval. Room temperature cw output powers exceeding 1.7 W have been demonstrated for broad area single element devices with highreflection/ antireflection coated mirror facets, mounted epi-side down. The latter result is a proof for the high power capabilities of these GaSb-based mid-ir diode lasers.

(In)GaAsN based heterostructures have been found to be promising candidates for the active region of 1.3 micron VCSELs. However, (In)GaAsN bulk layers and quantum wells usually demonstrate lower photoluminescence intensity than their nitrogen-free analogues. Defects associated with lower temperature growth and N-related defects due to plasma cell operation and possible nonuniform distribution of nitrogen enhance the non-radiative recombination in N-contained layers. We studied the photoluminescence intensity of GaAsN layers as a function of N content in MBE grown samples using rf-plasma source. Increasing the growth temperature to as high as 520 °C in combination with the increase in the growth rate allowed us to avoid any N-related defects up to 1.5% of nitrogen. Low-temperature-growth defects can be removed by post-growth annealing. We achieved the same radiative efficiency of GaAsN samples grown at 520°C with that of reference layer of GaAs grown at 600°C. Compositional fluctuations in GaAsN layers lead to characteristic S-shape of temperature dependence of photoluminescence peak position and this feature is the more pronounced the higher the amount of nitrogen in GaAsN. Annealing reduces compositional fluctuations in addition to the increase in the photoluminescence intensity. The results obtained are important for further improving the characteristics of InGaAsN lasers emitting at 1.3 micron.

The synthesis of HgTe nanocrystals (NCs), coated with a CdS shell, presumably results in the formation of HgTe/CdS, HgTe/CdHgS core-shell structures or separated CdHgS alloys. Photoluminescence (PL), continuous-wave (cw) and time-resolved optically detected magnetic resonance (ODMR) spectroscopy examined the magneto-optical properties of the dominating resonance aforementioned products. The cw ODMR measurements indicated that the NCs exhibit a band, centered at 0.39 Tesla, corresponding to an excited state electron (e) and hole (h) spin manifold, with total angular momentum (F=S+L) Fe=1/2 and Fh=3/2, respectively. Theoretical simulation of the ODMR band revealed an anisotropy of the g-factor, indicating the existence of trapped carriers' at a mixed Cd-Hg tetrahedral site, confirming the formation of an alloy component. The time-resolved ODMR measurements reveal a characteristic radiative decay time and spin-lattice relaxation time of these trapped carriers of hundreds of microseconds.

Melting and crystallization experiments of InGaSb were done under the reduced gravity condition (10−2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.