Mechanism of current flow in a Au-Ti-Al-Ti-n +-GaN ohmic contact in the temperature range of 4.2–300 K

The temperature dependence of the contact resistivity ρ _c (T) of Au-Ti-Al-Ti-n ⁺-GaN ohmic contacts is studied experimentally and substantiated theoretically in the temperature range T = 4.2–300 K. It is shown that the saturation portion of ρ _c (T) is observed in the low-temperature measurement region (4.2–50 K). As the temperature increases, ρ _c decreases by the exponential law. The experimental and calculated dependences ρ _c (T) are in agreement. The obtained results make it possible to conclude the field nature of the current transfer for the saturation region of ρ _c (T) and the thermal-field one, for the exponential region.     

Study of the Current–Voltage Characteristics of InAsSb-Based LED Heterostructures in the 4.2–300 K Temperature Range

Semiconductors - The results of a study in the temperature range 4.2–300 K of the current–voltage characteristics of light emitting diode (LED) heterostructures with an active region...     

Edge electroluminescence of the effective silicon point-junction light-emitting diode in the temperature range 80–300 K

The edge electroluminescence spectra of silicon point-junction light-emitting diodes with a p-n junction area of 0.008 mm² are studied at temperatures ranging from 80 to 300 K. Unprecedentedly high stability of the position of the spectral peak is observed at temperatures in the range between 130 and 300 K. The spectral characteristics of the light emitting diodes are studied at 80 K at different current densities up to 25 kA/cm². In contrast to the earlier reported data obtained at 300 K, the data obtained at 80 K do not show any noticeable Augerrecombination-related decrease in the quantum efficiency. From an analysis of the electroluminescence spectra at 80 K in a wide range of currents, it follows that radiative annihilation of free excitons is not a governing mechanism of electroluminescence in the entire emitting region in the base of the point-junction light-emitting diode at all currents used in the experiment.     

Light emitting diodes for the spectral range λ=3.3–4.3 µm fabricated from InGaAs and InAsSbP solid solutions: Electroluminescence in the temperature range of 20–180°C (Part 2)

Light-emitting diodes (LEDs) based on p-n homo-and heterostructures with InAsSb(P) and InGaAs active layers have been designed and studied. An emission power of 0.2 (λ=4.3 µm) to 1.33 mW (λ=3.3 µm) and a conversion efficiency of 30 (InAsSbP, λ=4.3 µm) to 340 mW/(A cm²) (InAsSb/InAsSbP double heterostructure (DH), λ=4.0 µm) have been achieved. The conversion efficiency decreases with increasing current, mainly owing to the Joule heating of the p-n homojunctions. In DH LEDs, the fact that the output power tends to a constant value with increasing current is not associated with active region heating. On raising the temperature from 20 to 180°C, the emission power of the (λ=3.3 and 4.3 µm) LEDs decreases, respectively, 7-and 14-fold, to become 50 (at 1.5 A) and 7 µW (at 3 A) at 180°C.     

InAsSb/InAsSbP double-heterostructure lasers emitting in the 3–4 µm spectral range

Our earlier reports concerning the fabrication by liquid-phase epitaxy and investigation of InAsSbP/InAsSb/InAsSbP double heterostructure lasers emitting at 3–4 μm are reviewed. The dependences of spectral characteristics and the spatial distribution of the laser emission on temperature and current are discussed. Lasing modes are shifted by 0.5–1.0 cm⁻¹ to longer wavelengths with increasing temperature. The tuning of the lasing modes by means of current is very fast (10⁻⁸–10⁻¹² s). With increasing current, the modes are shifted to shorter wavelengths by 50–60 ? at 77 K. The maximum mode shift of 104 ? (10 cm⁻¹) is observed at 62 K. The spectral line width of the laser is as narrow as 10 MHz. Abnormally narrow directional patterns in the p-n junction plane are observed in some cases in the spatial distribution of laser emission. The current tuning of lasers, due to nonlinear optical effects, has been modeled mathematically in good agreement with the experiment. Transmittance spectra of OCS, NH₃, H₂O, CH₃Cl, and N₂O gases were recorded using current-tuned lasers. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 12, 2001, pp. 1466–1480. Original Russian Text Copyright ? 2001 by Danilova, Imenkov, Kolchanova, Yakovlev. See [1].     

Optical properties of metamorphic GaAs/InAlGaAs/InGaAs heterostructures with InAs/InGaAs quantum wells,emitting light in the 1250–1400-nm spectral range

It is demonstrated that metamorphic GaAs/InAlGaAs/InGaAs heterostructures with InAs/InGaAs quantum wells, which emit light in the 1250–1400 nm spectral range, can be fabricated by molecular-beam epitaxy. The structural and optical properties of the heterostructures are studied by X-ray diffraction analysis, transmission electron microscopy, and the photoluminescence method. Comparative analysis of the integrated photoluminescence intensity of the heterostructures and a reference sample confirm the high efficiency of radiative recombination in the heterostructures. It is confirmed by transmission electron microscopy that dislocations do not penetrate into the active region of the metamorphic heterostructures, where the radiative recombination of carriers occurs.     

Current dependence of capacitance of germanium p +-p junctions in the temperature range of 290–330 K

The current dependence of differential capacitance of germanium p ⁺-p junctions with the p-region resistivity of 45, 30, and 10 Ω cm is investigated in the temperature range of 290–350 K. It is shown that the current dependence of the p ⁺-p-junction capacitance varies with an increasing junction temperature. At the temperature of 290 K, the capacitance decreases with an increasing reverse current, changes sign from positive to negative, and increases with the forward current. At 330 K, the capacitance decreases to the lowest positive value with an increasing reverse current and changes sign to negative with increasing the forward current. At 310 K, the p ⁺-p-junction capacitance can change the sign from positive to negative with increasing the forward and reverse current. It is assumed that the positive and negative p ⁺-p-junction capacitance is caused by the change in the junction-region charge by the external voltage.     

Stacked InAs/InGaAs quantum dot heterostructures for optical sources emitting in the 1.3 µm wavelength range

A method is proposed for growing stacked InAs/InGaAs self-organized quantum dots on GaAs substrates. The technique allows fabrication of structures exhibiting intense and narrow-line photoluminescence in the 1.3 μm wavelength region. The influence of growth conditions on structural and optical characteristics was studied. The proposed structures show promise in developing vertical-cavity surface-emitting devices. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 5, 2000, pp. 612–616. Original Russian Text Copyright ? 2000 by Maleev, Zhukov, Kovsh, Mikhrin, Ustinov, Bedarev, Volovik, Krestnikov, Kayander, Odnoblyudov, Suvorova, Tsatsul’nikov, Shernyakov, Ledentsov, Kop’ev, Alferov, Bimberg.     

An enhanced MOSFET threshold voltage model for the 6–300 K temperature range

An enhanced threshold voltage model for MOSFETs operating over a wide range of temperatures (6–300K) is presented. The model takes into account the carrier freeze-out effect and the external field-assisted ionization to address the temperature dependence of MOS transistors. For simplicity, an empirical function is incorporated to predict short channel effects over the temperature range. The results from the proposed model demonstrate good agreement with NMOS and PMOS transistors measured from fabricated chips.     

Fundamental spectra of optical functions for indium bromide in the energy range of 2–30 eV at 4.2 K

The spectra of sets of optical fundamental functions are determined for an indium-bromide crystal in the range of 0–30 eV at 4.2 K for the polarizations E ∥ a and E ∥ c. The calculations are carried out using experimental reflection spectra R(E) and several software packages. Their basic features are established.     

Light emitting diodes for the spectral range of λ=3.3–4.3 μm fabricated from the InGaAs-and InAsSbP-based solid solutions: Electroluminescence in the temperature range of 20–180°C

Light emitting diodes (LEDs) with λ_max=3.4 and 4.3 µm (t=20°C) were studied at elevated temperatures. It is demonstrated that LEDs operating in the temperature range t=20–180°C can be described using the classical concepts of injection radiation sources and the processes of charge carrier recombination. The temperature dependences of reverse currents in the saturation regions of current-voltage characteristics are consistent with the increase in the intrinsic-carrier concentration according to the Shockley theory. The emission spectra are described on the assumption of the direct band-to-band transitions, spherically symmetric bands, and thermalized charge carriers. The current-power characteristics are proportional to I ^3/2 suggesting that the contribution of the nonradiative Auger recombination is dominant. The radiation power decreases exponentially with the temperature which is characteristic of the CHSH and CHCC processes.     

Spectral characteristics of lasers based on InGaAsSb/InAsSbP double heterostructures (λ=3.0–3.6 µm)

It is shown that an increase in the internal losses beyond the lasing threshold in the lasers based on InGaAsSb/InAsSbP double heterostructures (wavelength range λ=3.0–3.6 µm, temperature T=77 K) causes the current-related shift of the laser mode to shorter wavelengths. This shift is as large as 80 cm^?1/A and can explain the broadening of the laser line from 5 to 7 MGz as the pump current increases.     

Bimodality in the Electroluminescence Spectra of InGaAs Quantum Well–Dot Nanostructures

Semiconductors - The polarization-resolved electroluminescence spectra of waveguide structures based on quantum well–dots are investigated in the temperature range of 60–300 K. It is...     

Quantum dot semiconductor lasers of the 1.3 μm wavelength range with high temperature stability of the lasing wavelength (0.2 nm/K)

Lasers that emit in the 1.3 μm wavelength range and include the active region based on InAs quantum dots were grown by the method of molecular-beam epitaxy and have been studied. The cavity includes a multilayer interference reflector, which brings about the fact that a large factor of optical confinement and low leakage losses are obtained only for the light propagating at some angle and, consequently, having a strictly definite wavelength. It is shown that, due to the use of such a waveguide structure, the temperature shift of the lasing wavelength is 0.2 nm/K, which is 2.5 times smaller than this shift in the lasers with quantum dots and with a conventional structure of the waveguide. The lasers with the stripe-contact width W = 10 μm exhibited the spatially single-mode emission, which verifies the advantages of the suggested nonconventional structure of the optical waveguide.

     

Electrical characterization and reliability of submicron SOI CMOS technology in the extended temperature range (to 300 °C)

I-V characteristics and reliability parameters for the set of hardened SOI MOSFET's with special layouts and tungsten metallization to provide additional thermal tolerance for high-temperature SOI CMOS IC's are investigated in the temperature range up to 300 °C. The reliability aspects under test for MOSFET's are threshold voltage shift, subthreshold slope and mobility degradation, gate leakage current rise; for tungsten metallization (contacts, conductor lines and vias) I-T and R-T characteristics, failure time. The SOI MOSFET standard compact SPICE model BSIMSOI with traditional temperature limit of 150 °C is modified to be used for CMOS IC simulation in the extended temperature range up to 300 °C. The results indicate that the 0.5–0.18 μm SOI MOSFET's with tungsten metallization have stable electrical behavior that makes them possible to be used during implementation of HT CMOS IC's (to 300 °C).     

Current–voltage and capacitance–voltage characteristics of Al Schottky contacts to strained Si-on-insulator in the wide temperature range

The electrical characteristics of Al/strained Si-on-insulator (sSOI) Schottky diode have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements in the wide temperature range of 200–400 K in steps of 25 K. It was found that the barrier height (0.57–0.80 eV) calculated from the I–V characteristics increased and the ideality factor (1.97–1.28) decreased with increasing temperature. The barrier heights determined from the C–V measurements were higher than those extracted from the I–V measurements, associated with the formation of an inhomogeneous Schottky barrier at the interface. The series resistance estimated from the forward I–V characteristics using Cheung and Norde methods decreased with increasing temperature, implying its strong temperature dependence. The observed variation in barrier height and ideality factor could be attributed to the inhomogeneities in Schottky barrier, explained by assuming Gaussian distribution of barrier heights. The temperature-dependent I–V characteristics showed a double Gaussian distribution with mean barrier heights of 0.83 and 1.19 eV and standard deviations of 0.10 and 0.16 eV at 200–275 and 300–400 K, respectively. From the modified Richardson plot, the modified Richardson constant were calculated to be 21.8 and 29.4 A cm⁻² K⁻² at 200–275 and 300–400 K, respectively, which were comparable to the theoretical value for p-type sSOI (31.6 A cm⁻² K⁻²).     

Voltage oscillations in the case of the switching effect in thin layers of Ge–Sb–Te chalcogenides in the current mode

The I–V characteristics obtained for layers of chalcogenide vitreous semiconductor of the Ge–Sb–Te system in the current-generator mode are investigated. The instability region, i.e., the region of conductivity oscillations, observed in the case of the switching effect under conditions of a set current is revealed. The key parameters describing these oscillations and the conditions of their occurrence are investigated in detail. Analysis of the obtained data shows that, to explain the oscillations in the instability region, it is necessary to take into account an increase in the current density and the process of heat exchange between the current filament that arises in the film upon switching and the environment.     

The temperature dependent analysis of Au/TiO2 (rutile)/n-Si (MIS) SBDs using current–voltage–temperature (I–V–T) characteristics

In this study, the main electrical parameters of Au/TiO₂(rutile)/n-Si Schottky barrier diodes (SBDs) were analyzed by using current–voltage–temperature (I–V–T) characteristics in the temperature range 200–380 K. Titanium dioxide (TiO₂) thin film was deposited on a polycrystalline n-type Silicon (Si) substrate using the DC magnetron sputtering system at 200 °C. In order to improve the crystal quality deposited film was annealed at 900 °C in air atmosphere for phase transition from amorphous to rutile phase. The barrier height (Φ_b) and ideality factor (n) were calculated from I–V characteristics. An increase in the value of Φ_b and a decrease in n with increasing temperature were observed. The values of Φ_b and n for Au/TiO₂(rutile)/n-Si SBDs ranged from 0.57 eV and 3.50 (at 200 K) to 0.82 eV and 1.90 (at 380 K), respectively. In addition, series resistance (R_s) and Φ_b values of MIS SBDs were determined by using Cheung's and Norde's functions. Cheung's plots are obtained from the donward concave curvature region in the forward bias semi-logarithmic I–V curves originated from series resistance. Norde's function is easily used to obtain series resistance as a function of temperature due to current counduction mechanism which is dominated by thermionic emission (TE). The obtained results have been compared with each other and experimental results show that R_s values exhibit an unusual behavior that it increases with increasing temperature.