Dynamical X-ray diffraction studies have been carried out for lattice-matched InGaAs/InP superlattices grown by modified molecular beam epitaxy (MBE) techniques. The (400) X-ray satellite pattern, which is predominantly affected by the strain modulation, was analyzed. The strain and thickness of the actual layers including the presence of strained interfacial regions were determined.

A non-destructive characterization technique featuring a hard X-ray Microprobe is demonstrated for lll-V semiconductor device structures. A GaAs FET with a 2 μm gate length is measured as a model sample of a thin film structure. X-ray scanning microscopic images of the FET are obtained by diffracted X-ray and fluorescence X-ray detection. Diffracted X-ray detection measures the difference in gate material and source or drain material as a gray level difference on the image due to the X-ray absorption ratio. Ni Ka fluorescence detection, on the other hand, provides imaging of 500 Å thick Ni layers, which are contained only in the source and drain metals, through non-destructive observation.

We have investigated the relaxation of intentionally mismatched layers of InxAl1−x-As on InP. The layers were grown by MBE and characterized by double-crystal x-ray diffraction (DCXRD) and variable azimuthal angle ellipsometry. Measurements of DCXRD epitaxial layer peak width show high crystalline quality for layers up to five times the Matthews-Blakeslee critical layer thickness. For thicker layers, relaxation occurs with a change in crystal symmetry from tetragonal to orthorhombic. We attribute this to an asymmetry in misfit dislocation density. Ellipsometry reveals optical anisotropy for mismatched layers in compression, but not in tension.

Optical Bragg reflectors consisting of the binaries AlAs and GaAs were investigated using double crystal topography and diffractometry. In undoped mirror stacks stress relaxation due to the formation of misfit dislocations was observed, which could be prevented by doping the stacks with 1018cm−3 silicon. In topographs taken in the substrate and different satellite reflections an unusual vanishing of the contrast of different segments of the misfit dislocations takes place, that shows these different segments to be located at different levels of the stack. The contrasts of the threading dislocations are quite similar in the substrate and the satellite reflections whereas the misfit dislocations change their contrast markedly.

Current difficulties of Atomic Layer Epitaxy (ALE) include relatively low growth rates and narrow process windows. Gas phase reaction, complex behavior of valve switching and purging times are suggested as the major causes [1,2]. We have used a movable X-shaped mechanical barrier to divide the growth chamber into four zones. Each zone supplies either source gas or purging hydrogen. If the barrier is positioned 0.5–2 mm from the wafer carrier, it can efficiently shear off the boundary layer and therefore reduce gas phase reactions. The substrate, constantly rotating beneath the barrier, is alternately exposed to group III or V sources by purging zones. The result is that process times are significantly reduced, saturated growth rate of 1 μm/hour is obtained and a relatively wide process window is observed. It was found that the growth mode was not purely ALE, due to source gas mixing which contributes an additional, possible kinetically limited, component of growth rate. However, this was also found to result in uniform film.

Quantum well interdiffusion has been employed, for the First time in the quaternary InGaAsP/InP system (grown lattice matched to InP substrates), in order to modify the as-grown, nominally square, shapes of single quantum wells so as to increase their bandgap energies. This was accomplished, in a spatially selective manner, by using low energy ion implantation through a mask to generate vacancies. Subsequent rapid thermal annealing drove these vacancies down to the quantum wells where their presence enhanced the thermally driven interdiffusion of atoms between the well and barrier layers. The goal of this work is to develop a simple process for the integration of optoelectronic devices with differing functions.

Microelectronic devices require deposition of sequences of thin epitaxial layers, with individual layer thicknesses in some instances specified to within tolerances of the order of inter-atomic spacings. Double crystal X-ray diffraction provides measurements of superlattice layer thicknesses to a resolution of the order of inter-atomic spacings, provided diffraction line shifts originating from substrate wafer misalignments are accounted for.

Fe (C5H5)2 and Fe (CO)5 were used as the 3d transition metal dopants in semi-insulating InP epitaxial layer grown by MOCVD. From the bright and dark field images of the TEM analysis, many precipitates were observed. Three extra peaks of the X-ray diffraction were found. The peaks of free-exciton recombination, donor-acceptor transition and the recombination of bound exciton with phonon emission were observed in the short wavelength range. Two Fe related peaks was observed at 0.7079 eV and 0.6897 eV. For a wide range (10–600) of In/Fe mole fraction, the resistivity keeps at high values (about 108 Ω -cm) and appears the highest resistivity of 5 × 108 Ω -cm for 1 μ m layer.

The crystalline quality of InAlAs layers, grown by Molecular Beam Epitaxy on (100) InP substrates, has been investigated by Transmission Electron Microscopy in order to study the influence of InAlAs growth temperature (Tg) on the density of structural defects present in the layers. Tg was varied from 300°C up to 530°C. The density of stacking faults and threading dislocations drops dramatically as Tg increas

The dependence of the luminescent properties of rare-earth impurities on the band structure of the host compound semiconductor has been investigated. Photoluminescence spectroscopy was used to characterize the optical properties of rare-earth doped Ini1−xGaxP layers prepared by metalorganic vapor phase epitaxy as a function of alloy composition. Thermal quenching of the Er3+, Yb3+, and Tm3+ related emission was observed over the temperature range of 15K to 360K with activation energies that depended on the alloy composition. From measurements of the thermally activated luminescence quenching, the energy levels of the isovalent erbium, ytterbium, and thulium in the alloys were determined. The variation of the position of the rare-earth related energy levels in the host semiconductor is explained in terms of a vacuum referred binding energy model that should have general applicability to other rare-earth doped semiconductor systems.

Thirty-period In0.28Ga0.72As(100Å)/GaAs (100Å) multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (lOO)-oriented GaAs substrate with a 0.5μm-thick InyGa1-yAs (0≤y≤0.28) buffer layer interposed between the QW layer and the GaAs substrate. The MQWs with y close to the average InAs mole fraction of the QW layer exhibited good crystalline quality. It indicates that the strain is well-balanced between the GaAs and In0.28Ga0.72As layer. A significant change in their photoluminescence spectra has been observed when annealed above 750δC by means of rapid thermal annealing, implying a structural disorder in the QW“region.

We present preliminary results aimed at investigating the effects of unprecracked arsine and trimethylgallium on the CBE (chemical beam epitaxy) growth of GaAs epilayers. We find that the growth rate rises linearly as the V/III ratio is increased when TMGa and arsine are used. All of the runs produced p-type material mainly due to carbon incorporation with the hole concentration typically of 1017 cm−3. The impurity content of the layers was found to depend distinctly on the pressure of TMGa. The significant drop in hole concentration is due in part to the hydrogen atoms generated from decomposed AsH3 which then aids in the removal of CH3 radicals on the surface. As a result of using unprecracked arsine for growth of the GaAs epilayers, we measure substantial improvements in their electrical and optical properties.

The optical properties of a quantum wire array which was successfully realized in a 4-nm-thick (GaAs)1/2 (AlAs)1/2 fractional-layer superlattice (FLS) are described. The FLS sample was grown by metalorganic chemical vapor deposition on a (001) vicinal GaAs substrate tilted 2 ° towards [110]. The nominal cross sectional size of the GaAs wires is 4×4 nm. Optical anisotropy in absorption, refractive index and photoluminescence was clearly observed by polarization spectroscopy at room temperature as well as lower temperatures.

We describe a novel instrument dedicated to making rapid angular-dispersive grazing incidence X-ray reflectivity measurements. A novel, automatic, optical technique for rapid specimen alignment, is incorporated into the control software. We discuss the information content of diffuse scattering data collected in non-standard modes. Examples of data are presented showing the application to the characterization of semiconductors and metal multilayers. The technique is shown to be particularly powerful for measurement of the thickness of epitaxial films of AlGaAs on GaAs less than 50 nm thick and where high resolution X-ray diffraction becomes impracticable. We demonstrate that, as the method is insensitive to dislocation density, high quality data can be taken rapidly from heavily relaxed multilayers. Minimum criteria for adequate information content in the data are explored and the effect of specimen curvature is examined.

This paper describes a compact production line microwave (approx. 10 GHZ) active layer sheet resistivity carrier mobility measurement instrument based on the invention from IBM Watson Labs by Dr. Norman Bras lau. [1]

The Measurement techniques and compound semiconductor wafer measurements will be described.

This paper describes the use of advanced circuitry nondestructive eddy current techniques to map compound semiconductors. Surface profiles, contour maps and diameter scans are obtained from the process wafers tested providing the necessary information to control the processes for maximum yield.

We will report on how the statistics and data analysis using sophisticated computer routines to study the radial uniformity of the compound semiconductors can be used for optimum output. Additionally, a review is presented of the basic principles of measurement and the applicable test methods and standards.

Important aspects that enable feedback to deposition and implant equipment enabling uniformity improvements are discussed. Specification improvements resulting from recent circuit and software additions and the measurement results are discussed.

This paper describes a useful measuring technique enabling Deep Level Transient Spectroscopy [DLTS] on compound semi-conductors. We will report on the methodology of DLTS measurements using newly available software for Miller Feedback Profilers. This method has the advantages of using the constant depth capabilities of the profiler. The combination instrument offers flexibility in limited clean room space.

This Poster describes the work done in a joint effort Research and Development Program with a leading University, with funding from the state, to develop a heterojunction bipolar transistor (HBT) epitaxial wafer screening tool. A computerized characteristics to HBT performance will be described.

Photoreflectance data from about twenty HBT wafers that have been grown and have had test transistors fabricated from the wafers will be analyzed to determine the bandgap of the epitaxial materials and the electric fields.

Comparison with previous works will be made in an attempt to reach a unified agreement in understanding that may lead to an ASTM test method.

Zinc doping is performed on the GalnP/AIGalnP multiquantum well (MQW) structure with the aim of dissolving the ordered atomic arrangement which results in higher quantum levels and therefore shorter lasing wavelengths. It is shown that the photoluminescence (PL) peak wavelength gradually shortens with doping and decreases by 20 nm when the hole concentration reaches 1×1018 cm−3, while the PL relative intensity becomes half that of an undoped MQW layer. Therefore, a moderate level of zinc doping of around 4∼5×1017 cm−3 is desirable to shorten the PL wavelength without decreasing the crystal quality. Transmission electron nano-diffraction patterns confirm that the ordered structure in the MQW layers disappears as the hole concentration increases. On the basis of this data, uniformly p-doped and modulation p-doped MQW laser diodes are fabricated and their characteristics are compared with the undoped MQW lasers. CW operation is achieved at wavelengths of 631 to 633 nm, which is 10 nm shorter than the 643 nm in an undoped MQW laser. Comparatively low threshold currents of 73 and 88 mA are attained for uniformly p-doped and modulation p-doped MQW lasers, respectively. However, they are about 20∼30 mA higher than those of the undoped MQW lasers. This results from the large overflow of electrons from the active layer, and the fact that the differential gain becomes smaller in the 630-nm band.

The possibilities of the optically detected impact ionisation (ODII) technique are demonstrated. It is shown how the ODII technique can be used to extract detailed spectroscopie information in thick InGaAs layers where resolved peaks from free excitons, bound excitons, and free-to-acceptor recombinations are obtained. In an investigation of single- and multiple-monolayer quantum wells of lattice-matched GalnAs in InP the experimental data show how the transfer of impact ionised electrons from the InP layers to the different InGaAs quantum wells, where they recombine as free excitons, can be studied. The recombination in a thicker quantum well (18 monolayer) shows a more complicated behaviour, and an explanation based on defect-related recombination, including bound-exciton and free-to-bound recombinations, is suggested.