[en] InP/InGaAsP-based heteroepitaxial structures constitute the major optoelectronic devices for state-of-the-art long wavelength optical fiber communication system.s Future advanced device structures will require thin heteroepitaxial quantum wells and superlattices a few tens of angstrom or less in thickness, and lateral dimensions ranging from a few tens angstrom for quantum dots and wires to a few μm in width for buried heterostructure lasers. Due to the increasing complexity of the device structure required by band-gap engineering, the performance of these devices becomes susceptible to any lattice imperfections present in the structure. Transmission electron microscopy (TEM), therefore, becomes the most important technique in characterizing the structural integrity of these materials. Cross-section transmission electron microscopy (XTEM) not only provides the necessary geometric information on the device structure; a careful study of the materials science behind the observed lattice imperfections provides directions for optimization of both the epitaxial growth parameters and device processing conditions. Furthermore, for device reliability studies, TEM is the only technique that unambiguously identifies the cause of device degradation. In this paper, the authors discuss areas of application of various TEM techniques, describe the TEM sample preparation technique, and review case studies to demonstrate the power of the TEM technique

[en] We report, for the first time, the identification of extrinsic dislocation loops lying on the {100} planes with 1/2 left-angle 100 right-angle types of Burgers vectors in a zinc blende structure in InGaAsP lattice matched to InP. These dislocation loops generated only in nonradiative recombination assisted point-defect motion process under intensed laser light, and form the left-angle 100 right-angle type dark line defects in degraded 1.3 μm wavelength laser diodes

[en] In this article, we report on the application of pyrometric interferometry to monitor the growth rate of (Al)GaN in situ during molecular-beam epitaxy. Since the growth rate of III-nitrides is very sensitive to the nitrogen flux, it is important to monitor the variation in growth rate from run to run. Using this method, we grew GaN/Al_xGa_1-xN quantum-well structures with well thicknesses between 10 and 40 Aa. The thicknesses of the quantum wells were confirmed by cross-sectional transmission electron microscopy measurements and found to be in good agreement with the corresponding growth rate determined in situ during the growth process

[en] Pt/Ti low resistance non-alloyed ohmic contacts to p-InP-based contact layers in photonic devices, formed by rapid thermal processing (RTP), have been studied. E-gun evaporated Pt/Ti metallization deposited onto 1.5 · 10¹⁹ cm^-3 Zn doped In_0.53Ga_0.47As yielded the best electrical performance. These contacts were ohmic as deposited with a specific contact resistance value of 3.0 · 10^-4Ωcm². RTP at higher temperatures led to decrease of the specific contact resistance to 3.4 · 10^-8Ωcm² (0.08Ωmm) as a result of heating at 450 degrees C for 30 sec. This heat treatment caused only a limited interfacial reaction (about 20 nm thick) between the Ti and the InGaAs, resulted in a thermally stable contact and induced tensile stress of 5.6 · 10⁹ dyne · cm^-2 at the metal layer but without degrading the adhesion. Heating at temperatures higher than 500 degrees C resulted in an extensive interaction and degradation of the contact

[en] Two low temperature metalorganic chemical vapor deposition growth techniques, the pre-cracking method and the plasma enhanced method, is discussed. The pre-cracking technique enables one to grow high quality epitaxial Hg_1-xCd_xTe on CdTe or CdZnTe substrates at temperatures around 200-250⁰C. HgTe-CdTe superlattices with sharp interfaces have also been fabricated. Furthermore, for the first time, the authors have demonstrated that ternary Hg_1-xCd_xTe compounds and HgTe-CdTe superlattices can be successfully grown by the plasma enhanced process at temperatures as low as 135 to 150⁰C. Material properties such as surface morphology, infrared transmission, Hall mobility, and interface sharpness are presented

[en] A stress-freezing technique is used to observe the stress distribution inside a cylindrical body produced by a coaxially loaded cylindrical punch. The flat end of the punch is pressed against the top surface of a vertical cylinder. After the stress is frozen in, a thin vertical diametric slice is prepared for photoelastic observation. The stress distribution is compared with theoretical results calculated for a semi-infinite body using the following two boundary conditions: uniform displacement of the punch and uniform pressure under the punch. The agreement is good at long distances (three times the punch radius) with either boundary condition. At short distances, the observed stress distribution is in between but close to the uniform displacement boundary condition. These results support the use of mixed stress distributions under the punch in a previous finite-element calculation of impressing creep velocities

[en] With X-ray diffraction techniques, it is possible to routinely measure lattice parameters to several parts in 10/sup 4/ for macroscopic specimens. However, measurements of lattice parameter changes for quaternary (InGaAsP) device structures several microns in width are not usually feasible with X-ray diffraction techniques. Convergent Beam Electron Diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), may be sensitive to these small, localized lattice parameter changes. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials. For this reason, the authors have chosen to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. For the active quaternary region of an electro-optical device structure, it is shown that this approach may be sensitive to a relative change in the lattice parameter as small as +-2 parts in 10/sup 4/, which is the uncertainty in the X-ray calibration measurements

[en] Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V(sub RB)) up to 550V and gt;2000V, respectively, have been fabricated. The on-state resistance, R(sub ON), was 6m(Omega)(center_dot) cm(sup 2) and 0.8(Omega)cm(sup 2), respectively, producing figure-of-merit values for (V(sub RB))(sup 2)/R(sub ON) in the range 5-48 MW(center_dot)cm(sup -2). At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and(ge)15 for the 2kV diodes. Reverse recovery times were and lt;0.2(micro)sec for devices switched from a forward current density of(approx)500A(center_dot)cm(sup -2) to a reverse bias of 100V

[en] This paper reports on dynamical X-ray diffraction studies that 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

[en] An abrupt transition in the growth mode is observed for epitaxial films of In P prepared by metalorganic molecular beam epitaxy. Below a minimum growth temperature, T^min_g, three-dimensional growth and kinetically controlled roughening are observed, with surface roughness showing two distinct power law regimes dependent on film thickness. The observed roughening is attributed to the presence of a Schwoebel-Erlich-type barrier to adatom motion across surface steps. From the dependence of T^min_g on the substrate misorientation, we are able to estimate an upper limit of 0.4-O.5 e V for this barrier. At temperatures higher than T^min_g, we observe smooth morphologies with the concurrent of localized defects associated with P-vacancies. The density of defects is strongly dependent on the thermodynamic and kinetic growth parameters. (author). 18 refs., 6 figs