Photonic crystal structures defined by interferometric lithography were etched into GaSb and AlGaAsSb with 90% Al content using Inductively Coupled Plasma (ICP) Reactive Ion Etching (RIE) with BCl3 and BCl3/Ar gas mixture. Effects of DC bias, hole diameter, etch time and gas composition, on the etch rate of GaSb were investigated. Hardened photoresist (PR) was used as an etch mask for the experiments.

The effect of increasing boron or phosphorus implant dose (i.e., 5×1013-5×1016 cm−2) and subsequent annealing (400-600°C for 3 hrs in N2) on the activation, diffusion and structure of germanium is studied in this work. The peak concentration of implant dose is ∼ 2×1021 cm−3. Secondary ion mass spectrometry (SIMS), spreading resistance profiling (SRP), high resolution X-ray diffraction (HRXRD), X-ray absorption fine structure (XAFS), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA) were used to characterize the implant and activation behavior. Boron is found to have a high solid solubility (i.e., > 2×1020 cm−3), even immediately after implant; while in contrast, phosphorus is limited to ∼ 1–2×1019 cm−3. Diffusion of phosphorus is also extremely extrinsic, while boron is practically immobile.

The effect of different oxygen species on the RF plasma-assisted molecular beam epitaxy growth of ZnO films has been investigated. By varying the geometry of the aperture plate and also the RF power, the relative atomic content in the discharge was altered, and this is found to be corre-lated to the film quality. Further, growth rate studies performed in tandem with in-situ laser interferometry suggest that stoichiometric conditions may not result in saturation of growth rates.

A nitridation mask on a GaAs surface was prepared using RF-MBE and its machinability by STM lithography was studied. A 5.2 nm thick crystal-like layer was formed at 350°C, and was modified by STM at a sample bias of ±80V with good size reliability, which was sufficiently fine for realizing dislocation-free heteroepitaxial growth of GaAs / Si. The mask was maintained up to 620°C under As flux exposure at 1.5 × 10−4 Pa.

GaNyAs1−x−yBix alloys were grown by molecular beam epitaxy (MBE) using solid Ga, Bi, and As sources and nitrogen radicals generated from N2 in rf plasma. To achieve Bi incorporation into the epilayer, As flux was adjusted in a limited range on the brink of As shortage on the growing surface. GaNyAs1−x−yBix alloys lattice-matched to GaAs substrates with different photoluminescence (PL) peak energies were obtained. The GaNyAs1−x−yBix alloy lattice-matched to GaAs turned out to have the structure of Ga(N0.34Bi0.66)zAs1−z. The PL spectra showed that the PL peak energy of GaNyAs1−x−yBix alloy decreased with increasing Bi and N contents with redshift coefficients of ∼62 meV/%Bi and ∼130 meV/%N, respectively, at room temperature. The temperature dependence of the PL peak energy for GaNyAs1−x−yBix in the temperature range of 150∼300 K is much smaller than that of InGaAsP. The temperature coefficients of GaNyAs1−x−yBix bandgaps were governed by the GaBi molar fraction and decrease with increasing GaBi molar fraction.

We have studied the effect of strain compensation in multiple stacking of InAs self-assembled quantum dots on GaAs (001) substrates grown by atomic hydrogen assisted RF-molecular beam epitaxy. The GaNxAs1−x material was used as a strain compensating spacer layer. We confirmed by high resolution x-ray diffraction measurements that a 40 nm GaN0.005As0.995 strain compensating layer provides compressive strain to compensate for tensile strain induced by 2.0 ML InAs quantum dots. Consequently, we achieved a multiple stack of InAs QDs up to 30 layers without formation of coalesced QDs, and the density of QDs exceeded 1012 cm−2.

ZnO thin films have been epitaxially grown on r-plane sapphire by RF-plasma-assisted molecular beam epitaxy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicate that the epitaxial relationship between ZnO and r-plane sapphire is (1120)ZnO // (1102)sapphire and [0001]ZnO // [1101]sapphire. Atomic force microscopy measurements reveal islands extended along the sapphire [1101] direction. XRD omega rocking curves for the ZnO (1120) reflection measured either parallel or perpendicular to the island direction suggest the defect density anisotropy along these directions. Due to the small lattice mismatch along the ZnO [0001] direction, few misfit dislocations were observed at the ZnO/Al2O3 interface in the high-resolution cross-sectional TEM image with the zone axis along the ZnO [1100] direction.

This paper describes the surface texturing mechanism on crystalline Si using hydrogen radicals generated by a tungsten hot filament. Inverted pyramid or labyrinthV groove structure could be obtained by particle deposition before etching. Mesh like tungsten particle layer, works as an etching mask against hydrogen radical, was obtained when silicon substrate was used. On the other hand, tungstem particles were not deposited as mesh like pattern when SiO2/Si substrate was used. The results suggest that evaporation of silicon hydrides from the silicon surface by hydrogen radical etching causes the mesh like pattern deposition of tungsten particles. Increase of filament current enables short time texturing process of less than 1 minute.

Silicon oxynitride (SiON) was deposited as a core layer on a silica (SiO2) under-cladding layer by using plasma enhanced chemical vapor deposition (PECVD). The refractive index of the SiON core layer was varied between 1.45 and 1.78 by changing the gas flow ratio of SiH4, N2O and NH3. Etching experiments were performed using a dry etching equipment to fabricate the SiON core. An optical planar waveguide with a core and under-cladding thicknesses of 6 μm and 8 μm, respectively, and a refractive index contrast (Δn) of 7 % has been fabricated.

N and B codoped 6H-SiC epilayers were grown by the closed sublimation method, the growth rate of which was as high as 100 mm/h. Donor acceptor (DA) pair emission at different temperatures was investigated for two samples with different B concentrations. The integrated photon count obtained from the photoluminescence (PL) spectra of the sample having high B concentration increases with temperature. To estimate the internal quantum efficiency, we measured the PL integrated photon counts of GaN at 10 K as a reference. The integrated PL photon count of 6H-SiC DA-doped epilayer at 250 K is almost comparable to that of GaN at 10 K, which is thought to be almost 100% because of the freezing of the nonradiative recombination at low temperature. This result implies that the internal quantum efficiency of the 6H-SiC DA-doped epilayer exceeds 95%.

The shallow donor impurities in ZnO with binding energies between 46 and 56 meV have been studied in great detail in the recent years. They give rise to neutral donor bound exciton recombinations with the A- and B-valence bands, show rotator states and two-electron-satellite transitions. These properties allowed to establish the excited state splittings of the donors as well as confirming Hayne's rule in ZnO. So far they all seem to be of extrinsic origin, hydrogen, aluminum, gallium and indium in order of increasing binding energy. For many years it was common sense that intrinsic defects would dominate the n-type conductivity of ZnO. Interstitial zinc as well as oxygen vacancies should be double donors, and in order to contribute to the n-type-conduction they should have shallow levels, and low formation energies to be abundant. In PL-measurements at T∼100 K on various ZnO samples, single crystals as well as thin films, a luminescence around 3.31 eV was detected. Due to its line shape and temperature behaviour it is identified as bound-to-free recombination. If we assume that the 3.31 eV band with its level at EC ∼ 130 meV is the ++/+ level of the zinc interstitial we calculate for the binding energy of the +/0 level ∼ 130 meV, i.e. around 33 meV. Undoped Zn-rich epitaxial films grown by CVD show a dominant I3 recombination at 3.367 eV which according to Haynes rule is consistent with a shallow donor level at 33 meV. Moreover, they have free n-type carrier densities of 2×1019 cm−3 and as revealed by SIMS the common donor impurities (Al, Ga, In) cannot account for the high carrier densities.

Diamond has various advantages as an electron emitter in addition to the low-threshold voltage, negative electron affinity (NEA), high thermal conductivity, high mechanical hardness, and high chemical stability. The difficulty in clarification of electron emission mechanism is preventing diamond from being used in the practical use. It is extremely difficult to identify the surface potential of the emitting diamond from conventional Emission current (I)- Anode voltage (V) characteristics. If one could measure the potential of the emitting surface, the band diagram of emitting diamond can be completed. The combined spectroscopy of XPS/UPS/FES specially built for this study, is one of the most powerful tool, which could identify the potential of the emitting surface. In this study, we have succeeded in observing the origin of field-emitted electrons using our combined XPS/UPS/FES system.

In this paper the preliminary results of incorporating a novel active layer into a GaN light emitting diode (LED) are discussed. Integration of colloidal CdSe quantum dots into a GaN LED active layer is demonstrated. The conductivity of the overgrowth was examined by circular transmission line method (CTLM). Effects on surface roughness due to the active layer incorporation are examined using atomic force microscopy (AFM). LED test devices were fabricated and electroluminescence was demonstrated, the devices exhibit higher turn-on voltages than would be expected for a CdSe active layer.

Methods for forming Ge epitaxial layer on Si (100) substrate have been vigorously sought due to potential applications of such structure as a virtual substrate for III-V devices on Si. Various methods were proposed to realize low threading dislocation density and smooth surface. To date, such methods involve more than one of thick (micrometer order) SiGe buffer growth process, high temperature annealing steps and CMP process, which could compromise reliability and suitability for production.

In this study, we report feasibility of a thin (in the order of 10nm) SiGe buffer layer to realize pure Ge epitaxial layer with good crystalinity, low threading dislocation density, and smooth surface without high temperature annealing steps and CMP process.

As a result, we achieved shorter time for growth of practical thickness of crystalline Ge on Si (100) substrate, and also get the high quality Ge epitaxial layer which has low threading dislocation density with very smooth surface.

Ge epitaxial layer and underlying thin SixGe1−x buffer layer were grown on Si (100) substrate using a cold wall UHV-CVD system. Source gases of Si and Ge were Si2H6 and GeH4, respectively. No carrier gas was used for this process. SiGe buffer layer was grown on Si(100) substrate at 450 – 520˚C. Two-step growth process was employed to grow Ge epitaxial layer on the buffer layer. Ge seed layer was grown at a low temperature (350–400˚C), followed by Ge thick layer growth at a high temperature (550–650˚C). XRD, TEM, EPD, and AFM were used for characterization of Ge epitaxial layer.

Optimization of growth temperature and source gas flow rate ratio enabled to obtain an effective buffer layer thinner than 10nm. The thin buffer layer realizes process time shortening, which is within 10min, and the smooth surface is realized without crosshatch structure. The buffer thickness is 1/160 to 1/1000 than that of previously known methods using thick SiGe buffer layers. Thin SiGe buffer also enabled process time shortening for Ge seed layer growth as two-dimensional Ge layer was formed faster on the thin SiGe buffer layer than on Si. XRD of the Ge seed layer showed 97% relaxation as grown and fully relaxed at 550˚C. The threading dislocation density of the top Ge layer was estimated below 1E7counts/cm2 by TEM and EPD.

The misfit dislocations oriented along [110] at the interface between the SiGe buffer layer and the Ge layer and the distances are 9.5nm constantly in cross-sectional TEM image. We are checking the surface roughness of the Ge epitaxial layer by using AFM.

Dislocation glide kinetics dictate in relaxed graded buffers a fundamental opposition between the defectivity and throughput. For state-of-the-art Si-based applications, the trade-off between defect level and wafer cost (inversely related to throughput) has made the insertion of SiGe graded buffers into production difficult. We aim to mitigate the trade-off by reporting two advances that enable simultaneous improvements in both defectivity and throughput. The first is use of a high growth temperature to allow very fast dislocation glide velocities and growth rates as high as 1.0 μm/min. The second is the use of “pre-threaded” Si substrates, substrates with an elevated density of threading dislocations. By having dislocation nucleation controlled by uniformly distributed substrate threading dislocations, instead of unpredictable heterogeneous sources, impediments to dislocation glide, such as dislocation bundles and pile-ups, are reduced. By incorporating both advances into SiGe graded buffer epitaxy, dislocation pile-up densities are reduced by nearly three orders of magnitude, threading dislocation densities are reduced by a factor of 7.4×, and wafer throughput is increased at least 33%.

Ga-doped n-type ZnO films were grown by molecular-beam epitaxy (MBE) on R-plane sapphire substrates. Material characterizations such as photoluminescence (PL), X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and Hall measurements were carried out to characterize the optical, structural, and electrical properties of the film. Photoconductor devices for ultraviolet (UV) light detection were fabricated by depositing Al (250 nm)/Ti (20 nm) ohmic metal contacts. Linear characteristics were obtained from current-voltage (I-V) measurements that showed response to UV and visible illumination. Voltage dependent photocurrent (PC) spectra and responsivity spectrum were obtained to characterize the detection capability of the device in the UV region.

Thin films of Co substituted ZnO and ZnCo2O4 were deposited on c-axis (0001) oriented Al2O3 substrates using pulsed laser deposition. The XRD results showed all the films were highly (002) oriented with a less intense peak of (311) for ZnCo2O4 thin film. Micro-Raman spectra of ceramic targets showed the modes related to wurtzite ZnO and spinel ZnCo2O4 structures. In thin films of Zn1−xCoxO no modes corresponding to ZnCo2O4 were detected. The intensity of E1(LO) and multiphonon peak at 584 and 540 cm−1 respectively, increased with increase in Co substitution. The optical absorption of the films showed that the band gap decreased with increase of Co concentrations at room temperature along with the sub-bandgap absorptions due to d-d transitions of Co2+. Similar sub-bandgap d-d transition was also observed in the absorption spectra ZnCo2O4 thin films. The highest saturated magnetization (0.2μB/Co) was obtained for 5%Co substituted ZnO.

Czochralski technique was employed in an attempt to grow a single crystal of the system ZnO-TeO2. A good quality grown crystal is expected to be transparent with a very light yellow color. The crystals exhibit a high resistivity of the order of 1013 Ω-cm. Different mole percentages have been tested for growth. Several attempts were performed to pull a single crystal. It was found that the best mole percentage of ZnO-TeO2 is 35.5:64.5. The pulled material grows uniformly, such that necking and conning are noticed. The pulled material contained multiple single crystals which were isolated and studied. Each one of them was transparent. Some properties will be presented. The pulled material of the 40:60 ZnO-TeO2 mole percentage returned four phases. Two of these phases are very uncommon.

The interests of low-k dielectric materials to reduce capacitance in multilevel metal interconnects of integrated circuits are well known in the semiconductor industry. Mechanical properties of low-k film are currently the main issues. Improved hardness and modulus are desirable because, when building a multilayered stack and doing sequential processing, films go through chemical mechanical planarization. In this proceeding, we reports the Young's moduli of the typical low k materials, and the effects of various factors for Young's moduli of materials, such as, structures of precursors, density, and porosity. Using atomistic molecular dynamics simulation with experimental measurements, the Young's moduli of films of amorphous silicon oxide in which 25% of Si-O-Si chains were replaced by Si-(CH3 H3C)-Si, Si-CH2-Si, Si-(CH2)2-Si, Si-(CH2)3-Si, Si-(CH2)4-Si, Si-(CH2)6-Si, were measured and analyzed. The predicted trends of Young's moduli of films formed by above precursors are in good consistent with those observed from experiments. The Young's moduli of materials are largely dependent on the densities of materials. Young's modulus of material increases as the density of the material increases. The chemical properties, chain length, and connectivity of material take effects on the Young's modulus of material. Given the same densities of material the smaller number of cavities per unit volume the material has, the lower Young's modulus it shows. Based on the results, the method of predict mechanical properties of materials by the conjunction of basic experimental measurements and atomistic simulation will be discussed.

We investigate a tunneling injection InP quantum-dot (QD) laser theoretically and experimentally. The device consists of a single compressively strained InP QD layer coupled closely to two tensile strained InGaP quantum wells (QWs). While most tensile strained QW lasers in this wavelength (red) range lase in the transverse-magnetic (TM) polarization, our QD laser lases in the transverse-electric (TE) polarization from the first excited state of the compressively strained QDs, which is coupled to the ground state of the tensile-strained InGaP QWs. When we measure TE and TM modal gain spectra, a typical QW gain evolution behavior is observed at low injection currents, which can be theoretically explained by the quasi-equilibrium of carrier distribution. When the injection current is increased near threshold, a TE gain narrowing and a simultaneous TM gain pinning are observed in the measured modal gain spectra, which cannot be explained via the quasi-equilibrium model. We propose a polarization-dependent photon-mediated carrier re-distribution in the QD-coupled-QW structure to explain this TE and TM gain evolution behavior. When the injection current is just below threshold, the strong carrier depletion via stimulated emission due to coupling between the InP QD and InGaP QW states plays an important role in carrier re-distribution, which depends on the optical transition energy and polarization. This polarization-dependent photon-mediated carrier re-distribution explains the TE gain narrowing and TM gain pinning behavior. To quantitatively demonstrate the photon-mediated carrier re-distribution near the threshold current, a set of coupled rate equations are solved taking into account the polarization-dependent stimulated emission processes. The calculated polarization power ratio based on the coupled rate equations explains the experimental observations.