Array of InGaAsSb light-emitting diodes (λ = 3.7 μm)

Spectral, current-voltage, and light-current characteristics of p-InAsSbP/n-InGaAsSb/n ⁺-InAs narrow-gap diode structures with 130 × 130 μm lateral dimensions of active elements are presented. The 2D distribution of light emitted by the samples fabricated in the form of emitting flip-chip 1 × 4 arrays is examined, including analysis of the emission uniformity. The limiting effective temperature created by an emitter of this type is determined.     

On the Current Dependence of the Injection Efficiency and the Relative Contribution of the Escape Rate and Internal Optical Loss to Saturation of the Power–Current Characteristics of High-Power Pulsed Lasers (λ = 1.06 μm)

Semiconductors - The results of numerical simulation of the current dependence of the efficiency of injection into the active area of a laser based on separate-confinement double heterostructures...     

Internal quantum efficiency of stimulated emission of (λ=1.55 µm) InGaAsP/InP laser diodes

The stimulated emission (η _i ^st ) of InGaAsP/InP separate-confinement double heterostructure lasers operating at λ=1.5–1.6 μm has been studied experimentally and theoretically. Laser heterostructures with a varied design of the waveguide layer were grown by MOCVD. The maximum internal quantum efficiency η _i ^st ≈97% was obtained in a structure with a double-step waveguide characterized by minimum leakage into the p-emitter above the generation threshold. The high value of η _i ^st is provided by low threshold and nonequilibrium carrier concentrations at the interface between the waveguide and p-emitter. The calculation yields η _i ^st values correlating well with the experimental data. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 2, 2003, pp. 243–248. Original Russian Text Copyright ? 2003 by Skrynnikov, Zegrya, Pikhtin, Slipchenko, Shamakhov, Tarasov.     

Temperature dependence of the threshold current density in semiconductor lasers (λ = 1050–1070 nm)

The temperature dependences of the threshold current density and threshold concentration in semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with an extended waveguide have been studied (wavelengths ?? = 1050?C1070). It is shown that the temperature dependence of the threshold current density in semiconductor lasers becomes markedly stronger at above-room temperatures, which is due to temperature-induced carrier delocalization into the waveguide layers of a laser heterostructure. It was found that the sharp decrease in the thermal stability of the threshold current density with increasing temperature correlates with the coincidence of the Fermi level with the conduction-band bottom of the waveguide layer in the laser heterostructure. It is experimentally demonstrated that an increase in the energy depth and number of quantum wells in the active region of a semiconductor laser improves the thermal stability of the threshold current density. It is demonstrated that the characteristic parameter T ₀ attains a value of 220 K in the temperature range from ?20 to +70°C.     

Thermal delocalization of carriers in semiconductor lasers (λ = 1010–1070 nm)

The temperature dependences of the emission characteristics of semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures (wavelengths ?? = 1010?C1070 nm) have been studied. It was found that, in the continuous-wave mode, the main mechanism of ??saturation?? of the light-current characteristic with increasing temperature of the active region is carrier delocalization into the waveguide layer. It was experimentally demonstrated that the thermal delocalization of carriers depends on the energy depth of the quantum well (QW) in the active region. It is shown that the minimum internal optical loss at 140°C is obtained in laser structures with the largest energy depth of the QW of the active region.     

The temperature dependence of internal optical losses in semiconductor lasers (λ = 900–920 nm)

The temperature dependences of radiative characteristics of semiconductor lasers based on asymmetric heterostructures of the separate confinement with an extended waveguide fabricated by MOCVD epitaxy (the emission wavelength λ = 900–920 nm) are studied. It is established that the threshold concentration in the active region and waveguide layers of the laser heterostructure of the separate confinement increases in the CW lasing mode as the pumping current and temperature of the active region are increased. It is established experimentally that, in the temperature range of 20–140°C, the stimulated quantum yield remains unchanged. It is shown that the temperature delocalization of charge carriers leads to an increase in the carrier concentration in the waveguide layers of the laser heterostructure. The total increase in internal optical losses due to scattering by free charge carriers in the layers of the active region and waveguide layers of the laser heterostructure leads to a decrease in the differential quantum efficiency and to saturation of the watt-ampere characteristic of semiconductor lasers in the continuous lasing mode.     

Influence of rapid high-temperature anneals on the photoluminescence of erbium-doped GaN in the wavelength interval 1.0–1.6 µm

The influence of rapid-anneal conditions and subsequent coimplantation of oxygen ions on the photoluminescence of erbium ions implanted with an energy of 1 MeV and dose of 5×10¹⁴ cm⁻² in MOCVD-grown GaN films is investigated. The erbium photoluminescence intensity at a wavelength ∼ 1.54 μm increases as the fixed-time (15 s) anneal temperature is raised from 700 °C to 1300 °C. The erbium photoluminescence intensity can be increased by the coimplantation of oxygen ions at anneal temperatures in the indicated range below 900 °C. The transformation of the crystal structure of the samples as a result of erbium-ion implantation and subsequent anneals is investigated by Raman spectroscopy. Fiz. Tekh. Poluprovodn. 33, 3–8 (January 1999)     

The forward bias current density–voltage–temperature (J–V–T) characteristics of Al–SiO2–pSi (MIS) Schottky diodes

Metal–insulator–semiconductor Schottky diodes were fabricated to investigate the tunnel effect and the dominant carrier transport mechanism by using current density–voltage (J–V) and capacitance–voltage (C–V) measurements in the temperature range of 295–370?K. The slope of the ln?J–V curves was almost constant value over the nearly four decades of current and the forward bias current density J is found to be proportional to J_o (T) exp(AV). The values of N_ss estimated from J–V and C–V measurements decreased with increasing temperature. The temperature dependence of the barrier heights obtained from forward bias J–V was found to be entirely different than that from the reverse bias C–V characteristics. All these behaviours confirmed that the prepared samples have a tunnel effect and the current transport mechanism in the temperature range of 295–370?K was predominated by a trap-assisted multi-step tunnelling, although the Si wafer has low doping concentration and the measurements were made at moderate temperature.     

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.     

Optical Properties of Tellurium-Based Chalcogenide Alloys in the Far Infrared Region (λ > 30 μm)

Ternary telluride alloys of Ge–Se(Sb)–Te and Si–Ge(Ga)–Te systems are synthesized in glassy and crystalline states for use in the terahertz frequency range. The transmission spectra of the obtained alloys are measured and studied in a wide wavelength range from 0.75 to 300 μm. The possible mechanisms of their formation are discussed. A comparative analysis of the results shows that the Ge₁₄Sb₂₈Te₅₆ alloy of the GST system is most promising. Its phonon spectrum is in the range of 40–280 cm^–1, limiting the long-wavelength transmission window of this alloy by 35 μm. Optimization of the Ge₁₄Sb₂₈Te₅₆ composition, the removal of impurities, and heat treatment will promote a further decrease in the absorbance in the far-infrared spectrum of this alloy.     

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.     

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.     

High-temperature(T = 80℃) operation of a 2μm InGaSb-AlGaAsSb quantum well laser

正An InGaSb/AIGaAsSb compressively strained quantum well laser emitting at 2μm has been fabricated. An output power of 82.2 mW was obtained in continuous wave(CW) mode at room temperature.The laser can operate at high temperature(T = 80℃),with a maximum output power of 63.7 mW in CW mode.     

InGaAs/InP heterostructures with strained quantum wells and quantum dots (λ=1.5–1.9 µm)

Strongly strained In_xGa_1−x As/In_0.53Ga_0.47As/InP heterostructures with indium content x=0.69−1.0 in the active region were investigated experimentally and theoretically. Two types of structures were obtained by vapor-phase epitaxy from metalorganic compounds: 1) with isolated compression-strained quantum wells and 2) with self-organized nanosize InAs clusters (quantum dots). The temperature dependence of the quantum radiation efficiency of samples with quantum wells in the temperature range 77–265 K is characterized by T ₀=43 K. One reason for the low value of T ₀ is electron delocalization in the active region. The maximum radiation wavelength obtained in structures with quantum dots is 1.9 μm at 77 K. Fiz. Tekh. Poluprovodn. 33, 1105–1107 (September 1999)     

High-power diode lasers (λ = 1.7–1.8 µm) based on asymmetric quantum-well separate-confinement InGaAsP/InP heterostructures

Advantages of the concept of high-powered semiconductor nanoheterostructure lasers for the spectral range 1700–1800 nm, grown by MOCVD in the InGaAsP/InP solid solution system, have been experimentally demonstrated. It has been found that using an expanded waveguide enables reduction to 2 cm^?1 of the internal optical loss in quantum-well asymmetric separate-confinement double InGaAsP/InP heterostructures emitting at a wavelength of 1.76 µm. The heterostructures developed have been used to create multimode lasers with a room-temperature CW output power of 2.5 W in an aperture of 100 µm. It is shown that use of highly stressed quantum-well InGaAs layers as the active region makes it possible to obtain characteristic temperatures T ₀ = 50–60 K.     

Temperature dependent of the current–voltage (I–V) characteristics of TaSi2/n-Si structure

Tantalum silicide (TaSi₂) thin films were deposited on n-type silicon single crystal substrates using a dual electron-gun system and with Ta and Si targets. The electrical transport properties of the TaSi₂/n-Si structures were investigated by temperature-dependent current–voltage (I–V) measurements. The temperature-dependent I–V characteristics revealed that the forward conduction was determined by thermionic-emission and space-charge-limited current mechanisms at low and high voltage respectively. On the other hand, the reverse current is limited by the carrier generation process.     

Temperature dependence of the threshold current in quantum-well WGM lasers (2.0–2.5 μm)

The temperature dependence of the threshold current and emission spectra of disk-shaped quantum-well whispering-gallery mode (WGM) lasers is studied in the temperature range of 80–463 K in which the laser emission wavelength increases from 2 to 2.5 μm. It is shown that lasing is observed up to 190°C. Radiative recombination is dominant up to a temperature of 300 K, and nonradiative Auger recombination, in which a recombining electron gives energy to another electron, is so at higher temperatures. The spin-orbit split-off valence subband is not involved in recombination processes, which is attributed to mechanical compression of the quantum-well material.     

InGaAsSb(Gd)/InAsSbP double heterostructure lasers (λ=3.0–3.3 µm) for diode laser spectroscopy

Data on threshold currents, the differential quantum efficiency, the emission spectrum, current tuning, and radiation power of mesastripe InGaAsSb(Gd)/InAsSbP double heterostructure lasers with λ=3.0–3.3 µm and a cavity length of 70–150 µm in a temperature range of 50–107 K are reported. In the experiments, the threshold currents I _th<10 mA, a total output power of 0.5 mW/facet, and a single-mode power of 0.43 mW at 77 K in the cw regime were obtained. Lasers operated in the single-mode regime at currents I≤6I _th, the spectral purity was as high as 650: 1, the tuning rate was 210 cm^?1/A, and the tuning range was 10 cm^?1 wide. An example of methane detection at 3028.75 cm^?1 is presented.     

A compare of electrical characteristics in Al/p-Si (MS) and Al/C20H12/p-Si (MPS) type diodes using current–voltage (I–V) and capacitance–voltage (C–V) measurements

In this study, both the metal-semiconductor (MS) and metal-polymer-semiconductor (MPS), (Al/C₂₀H₁₂/p-Si), type Schottky barrier diodes (SBDs) were fabricated using spin coating method and they were called as D₁ and D₂ diodes, respectively. Their electrical characterization have been investigated and compared using the forward and reverse bias I–V and C–V measurements at room temperature. The main electrical parameters such as ideality factor (n), reverse saturation current (I_o), zero-bias barrier height (Φ_Bo), series (R_s) and shunt (R_sh) resistances, energy dependent profile of interface states (N_ss), the doping concentration of acceptor atoms (N_A) and depletion layer width (W_D) were determined and compared each other and literature. The rectifying ratio (RR) and leakage current (I_R) at ±3 V were found as 2.06×10³, 1.61×10⁻⁶ A and 15.7×10³, 2.75×10⁻⁷ A for D₁ and D₂, respectively. Similarly, the R_s and R_sh values of these diodes were found as 544 Ω, 10.7 MΩ and 716 Ω and 1.83 MΩ using Ohm’s Law, respectively. In addition, energy and voltage dependent profiles of N_ss were obtained using the forward bias I–V data by taking into account voltage dependent effective barrier height (Φ_e) and n and low-high frequency capacitance (C_LF–C_HF) methods, respectively. The obtained value of N_ss for D₂ (MPS) diode at about the mid-gap of Si is about two times lower than D₁ (MS) type diode. Experimental results confirmed that the performance in MPS type SBD is considerably high according to MS diode in the respect of lower values of N_ss, R_s and I_o and higher values of RR and R_sh.     

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).