We demonstrate a Si-based light-emitting diode (LED) with MHz modulation capability containing a certain class of light-emitting defects in the active region. The emission spectra are characterized by a narrow peak centered at 900 meV (1377 nm), hereafter referred to as E-line, which is attributed to the {311} defects inherent to cubic crystals with the diamond sublattice. The luminescence intensity of the E-line was found to go through a maximum around 20K persisting above 150 K. In spite of the decay lifetimes even longer than 1μs, 31% amplitude modulation was achieved for 1-MHz rectangular pulses at 20 K while near 10-MHz bandwidth was obtained for dynamic operation with modulated pulse widths.

GaAs based metamorphic and pseudomorphic high electron mobility transistors (HEMTs) under DC and thermal stress were studied. InAlAs/InGaAs MHEMTs grown on GaAs substrates were stressed at a drain voltage bias of 2.7V for 36 hours as well as thermally stressed at 250°C for 36 hours. Under both stress conditions, the drain current density decreased about 12.5%. The gate current, however, increased more after the thermal storage as opposed to DC bias. Reaction of the Ohmic contact with the underlying semiconductor was the main cause of degradation after thermal stressing. Transmission electron microscopy verified that gate sinking occurred in devices that underwent DC bias stressing. InGaAs pHEMTs that received a 1000 hour lifetime stress test from a commercial vendor showed similar degradation as virgin devices when stressed under DC bias for 24 hours. Virgin devices that were thermally stressed while undergoing DC bias showed minimal degradation up to 120°C, but exhibited catastrophic failure at 140°C.

A detailed description of the phenomenon of catastrophic optical-damage (COD) in short (380μm cavity-length), 12μm aperture, proton-bombarded, double-heterostructure laser-diodes with uncoated facets was first presented in 1974. In these devices, COD generally initiates at the facets due to high optical-power density and propagate along transverse-mode filaments. To achieve reliable operation at high optical-power, broad-area laser-diodes have evolved to long (several-millimeter cavity-length), wide-aperture (50-200μm), dielectric-defined, broadened-waveguide, separate-confinement, double-heterostructure, quantum-well laser-diodes with coated, passivated facets. COD in these devices involve both transverse modes and ring-cavity modes.

We have studied the effect of thin metal coatings on the electron emission characteristics of self-assembled silicon microstructures with nearly identical sharp features. We have employed a common template of spikes produced by fs-laser self-driven structuring of Si on which several different metals have been deposited. We find that, in the pristine state and in vacuum conditions achievable in device applications, all metal coatings do not result in marked change of either the minimum electric field necessary for emission or the maximum obtainable current density. In contrast, the durability of the emitters depends strongly on the metal used and is always enhanced with respect to bare Si. Furthermore, no signs of degradation were found within the 3-day time scale of our experiments with gold and chromium. On the contrary, these two metal coatings resulted in emission characteristics improving with time in typical operation conditions.

The Low Frequency Noise (LFN) characteristics of Organic Light Emitting Diodes (OLEDs) were investigated in relation to device degradation. The standard layer structure of indium tin oxide (anode), hole transport layer, Alq3, Lithium Fluoride and Aluminium (cathode) was used. With duration of operation, the device degradation is characterized by an eventual drop in the luminance level and the electroluminescence efficiency. Additionally, the driving voltage at a fixed current and the LFN increase gradually during device degradation, accompanied with the formation of non-emissive areas (dark spots). It is found that the coefficient of correlation between voltage fluctuations across the device and low frequency fluctuations of the optical signals remains constant for an initial period and then decreases exponentially with duration of operation and is a sensitive parameter to predict OLED device lifetime. For a number of OLEDs driven at constant current, the device with higher initial correlation coefficient possesses a longer lifetime. The direct relation between LFN correlation and device lifetime can be explained by carrier recombination mechanisms at the microscopic level. An increase in trap density can reduce the internal radiative recombination rate which at the macroscopic level is reflected by a decrease in the correlation coefficient.

To update the status of knowledge on the recombination-enhanced dislocation glides (REDG) in semiconductors, which is one of the causes of serious degradation in bipolar devices, research progress achieved for the last decade has been surveyed. Rather than presenting a complete review over a wide range of material systems, a particular attention has been paid to the REDG effect in 4H-SiC for which a lot of information has been accumulated owing to extensive studies. Although the REDG effect exhibits features that could be interpreted in terms of the phonon-kick mechanism, conclusive proof is still lacking.

Degradation processes in high power broad-area InGaAs-AlGaAs strained quantum well lasers were studied using electron beam-induced current (EBIC) techniques, time-resolved electroluminescence (TR-EL) techniques, and deep-level transient spectroscopy (DLTS). Accelerated lifetests of the broad-area lasers yielded catastrophic failures at the front facet and also in the bulk. EBIC was employed to study dark line defects generated in degraded lasers stressed under different test conditions. TR-EL was employed to study the intra-cavity intensity distribution in real time as devices were aged. DLTS was employed to study deep electron traps in both pristine and degraded laser diodes. Lastly, we present a possible scenario for the initiation of bulk degradation in the broad-area lasers.

Photoluminescence (PL) spectroscopy is a powerful technique for probing the structures of many types of III-V semiconductor materials. When a semiconductor material is excited at a particular wavelength, electron-hole pairs are generated. The most intense radiative transition is between the conduction band and valence band, and this measurement is used to determine the material band gap. Radiative and non-radiative transitions in semiconductors also involve localized defect levels. The photoluminescence energy associated with these levels can be used to identify specific defects, and the amount of photoluminescence can be used to determine their concentration, and thus predict device quality. At ambient temperatures, the PL signal is typically broad, as much as 100 nm in width. When cooled, structural details may be resolved, and a small spectral shift between 2 samples may represent a change in a structural parameter. Thus a system with high spectral resolution is required.

In this paper, a modular Low Temperature Photoluminescence system (LTPL) for measuring optical band gap as a function of temperature is described. Results show that the optical band gap shifts towards higher energy as the sample temperature decreases.

We present a novel, simple, and accurate approach based on low frequency voltage fluctuations to determine the averaged carrier lifetime in semiconductor materials and devices. This technique serves to address the limitations faced by existing techniques that use light as the excitation source for lifetime measurement. In this paper, the minority carrier lifetime is inferred from the 1/f low frequency noise profile exhibited by the device during low current operation. The current dependence of the power spectral density and its relation to minority carrier lifetime is modeled and derived directly giving a current dependent carrier lifetime. This technique is solely based on the electrical noise and no light source is required for excitation. The low frequency noise can be easily acquired without significant distortion via a signal analyzer as long as there is a sufficiently good Ohmic contact between the probe and the device under test, and that the device is sufficiently shielded from the influence of EMI. This technique has lower crosstalk, fewer fitting parameters, is low cost and allows the lifetime to be extracted directly from data collected at lower frequencies. These characteristics make our method useful in encapsulated devices, applicable on wafers and devices in

By launching new processes introduced by nano science into much more conventional industrial applications fast, robust and economical reasonable inspection methods are required for process control and quality assurance. Coming from high tech industries e.g. semiconductor industries the methods available for thin film characterization and quality control are complex and often require scientific skilled personal. High frequency eddy current spectroscopy in reflection or transmission configuration allows a contactless measurement of e.g. copper thin films on silicon with a thickness resolution better that 5 nm. Due to the insensitivity of the transmission mode to dislocations or slight tilting of the sample the high frequency eddy current method is a practicable method for thin film characterization under industrial environment.

Indium Gallium Nitride (InxGa1-xN) alloys are currently playing an ever increasing role in optoelectronic devices as the bandgap of such alloys can theoretically be tuned between 0.7eV and 3.4eV–covering the entire visible spectrum. Although growth of high quality InxGa1-xN alloys with high indium mole fractions are difficult or presently unattainable, InGaN alloys are still a viable choice for light emitters and detectors over the visible (blue/green) to ultraviolet spectrum. However, many inherent problems during InGaN growth via Metal Organic Vapor Phase Epitaxy (MOVPE) arise due to the large lattice mismatch and low miscibility between GaN and InN–leading to the formation of Inverted Hexagonal Pyramid (IHP) defects at the termination of threading dislocations. Additionally, growth of InGaN at lower temperatures to promote increased indium incorporation results in poor surface morphology. Several methods such as strained layer superlattices and low mole fraction InGaN layers before the growth of the InGaN/GaN MQW structures have been shown to relive strain in the MQWs, thus reducing the density of IHP defects and/or improving the optical output characteristics. This work focuses on the application of GaN monolayer insertions during InGaN quantum well growth via Metal Organic Vapor Phase Epitaxy (MOVPE) as a means to reduce the IHP defect density and passivate effects on surface roughness while observing variations in indium concentration. Observations include the reduction of IHP defect density by nearly twofold as the number of GaN monolayer interruptions increase from zero to three while sustaining only slightly lower effective indium concentrations.

Reliability and performance of ultraviolet light emitting diodes have suffered due to the high dislocation density of the AlN and high Al-content AlxGa1-xN layers when grown on foreign substrates such as sapphire. The development of pseudomorphic layers on low dislocation density AlN substrates is leading to improvements in reliability and performance of devices operating in the ultraviolet-C (UVC) range. One major improvement is the ability to operate devices at much higher current densities and input powers than devices on sapphire substrates. This is due to the better thermal properties and lower dislocation density of devices on AlN substrates. Devices with active area of 0.001 cm2 emitting at ∼265 nm have been measured for their reliability and change in power output over time at input currents of 20 mA (20 A/cm2), 100 mA (100A/cm2) and 150 mA (150 A/cm2). When operating at currents of 20 mA over 3500 hours of consecutive operation has been demonstrated with typical decay of ∼27% over the 3500 hours. Extrapolating the decay with a linear fit gives a L50 (time to 50% of initial power) of ∼5000 hrs. However it is desirable to be able to model the decay to better understand the kinetics and better understand the mechanisms. In order to do this, the lifetime at 20 mA and 100 mA were modeled using an exponential decay function, square root transformation and a log transformation to both be able to fit the experimental data and predict future performance.

With the continuing scaling in device sizes, sputtered copper is not expected to achieve the conformality and surface coverage requirements to be an effective seed layer for electrochemical deposition in sub-32nm features. Additionally, the metallization demands of high aspect ratio TSVs in 3D-architectures pose similar challenges. In this work, a manufacturable low temperature Cu PE-ALD process has been developed employing a novel O and F-free precursor. The ALD process conditions are correlated with key film properties, including deposition rate, composition, step coverage, and resistivity. Additionally, the influence of precursor substituents on the deposition rate and preliminary integration performance are discussed.

An experimental study on mid-infrared intersubband absorption in InGaAs/GaAsSb multiple quantum wells grown lattice-matched to InP substrates by molecular beam epitaxy is presented. Intersubband absorption in a broad wavelength region (5.8 - 11.6 μm) is observed in multiple quantum well samples with well widths ranging between 4.5 and 12 nm. A conduction band offset at the InGaAs/GaAsSb heterointerface of 360 meV gives an excellent agreement between the theoretically calculated ISB transition energies and the Fourier-transform infrared spectroscopy measurements over the whole range of well widths under investigation. Two kinds of intersubband devices based on the InGaAs/GaAsSb material system are presented: a quantum well infrared photodetector operating at a wavelength of 5.6μm and an aluminum-free quantum cascade laser. The presented quantum cascade laser emits at a wavelength of 11.3 μm, with a threshold current density of 1.7 kA/cm2 at 78 K.

Reliability testing often manifests device weaknesses and failure mechanisms. As new materials and structures are developed, creative and different testing is often necessary to determine reliability. We are developing an in-house reliability test system that will provide the necessary testing flexibility of HEMT devices so researchers can pinpoint defects and vulnerabilities. Using commercial off-the-shelf (COTS) power supplies and data acquisition equipment, a custom control system allows for many different tests: DC and RF, temperature, step/stress/recovery, high-speed pulse, and optical pumping, as well as combinations and automated sequencing of these tests. This flexibility allows for the creation of new test types as failure mechanisms are understood. The initial station will provide for the simultaneous, independent testing of 16 devices. This paper outlines the system design and capabilities, the motivation for the system, and some results from different tests.

We investigated triple ion implanted 4H-SiC BJT with etched extrinsic base regions. To remove the defects induced by ion implantation between emitter and base regions, the characteristics of triple ion implanted 4H-SiC BJT were significantly improved. Maximum common current gain was improved from 1.7 to 7.5.

We have demonstrated that scanning nonlinear dielectric microscopy (SNDM) exhibited high performance and high resolution in observing the dopant concentration profile of transistors. In this study, good quantitative agreement between the SNDM signals and dopant density values obtained by SIMS in standard Si samples, which dopant concentrations have been calibrated. We succeeded in visualizing high-resolution dopant profiles in n- and p-type MOSFET with 40 nm gate channels. It is considered that SNDM would be an effective method in measuring the quantitative two-dimensional dopant profiles of transistors. Finally, we have succeeded in detecting the dopant profiles of SRAM memory cell transistors.

A thermomechanical model to explain the formation of dark defects in AlGaAs high power laser bars is presented. The local heating at facet defects due to nonradiative recombination and self-absorption of photons induces thermal stresses capable of producing a local plastic deformation and subsequent degradation of the device. The output power density thresholds calculated are in agreement with the data reported in the literature for these lasers.

To update the status of knowledge on the recombination-enhanced dislocation glides (REDG) in semiconductors, which is one of the causes of serious degradation in bipolar devices, research progress achieved for the last decade has been surveyed. Rather than presenting a complete review over a wide range of material systems, a particular attention has been paid to the REDG effect in 4H-SiC for which a lot of information has been accumulated owing to extensive studies. Although the REDG effect exhibits features that could be interpreted in terms of the phonon-kick mechanism, conclusive proof is still lacking.

TiN provides a good template layer for the epitaxial SrTiO3 (001) growth on Si(001) single crystal substrates by RF sputtering. However, TiN template layer was oxidized into TiO2 during the subsequent sputtering process of electrodes of SrRuO3. The effect of Ru ion catalyzed oxidation and delamination of the TiN layer has been studied using transmission electron microscopy (TEM) and high-resolution transmission electron microscope (HRTEM). The epitaxial orientation relationship of the SrRuO3 and SrTiO3 was reserved to be cube on cube with respect to Si and the crystal quality of the SrRuO3/SrTiO3 film remained even when the TiN template layer was oxidized. The stress in the thin film of SrRuO3/SrTiO3/TiN structure could be determined from the buckle shape in both plan view and cross sectional TEM images.