Auger recombination in strained quantum well InAlAsSb/GaSb structures for 3–4 µm lasers

A detailed discussion is given for the x-ray rocking curve analysis of semiconductor heterointerfaces and strained quantum wells using x-ray interferometry. It is shown that for a single beteroepitaxial layer sample and a multiple quantum well sample, the heterointerface where the composition changes in both anion and cation sublattices can be studied with a half monolayer sensitivity by analyzing the x-ray rocking curve profile. Such sample systems include GaInAs/InP, InGaSb, GaInP/GaAs, ZnSe/GaAs, etc. A simple kinematical diffraction principle involved in the x-ray analysis is explained. Namely, the relative phase difference between the reflection amplitudes of any two layers depends on the total sum of strain (or mismatch)-thickness products over the intervening layers and interfaces. The x-ray interferometry is also effective in measuring the strain-thickness product of strained quantum wells. Experimental data and analysis results are presented for a series of functional device structures having a strained quantum well. For a more complicated sample structure which involves both a (strained) quantum-effect layer and gained interfaces, it is shown that the x-ray interferometry is only capable of providing the total strain-thickness product over the quantum layer and the surrounding interfaces, but no detailed information about the interface grading can be gained frommore » the rocking curve analysis alone if only one isolated sample is measured. An experimental data of such a sample, 0.3{mu}m-GaAs/100{Angstrom}-GaInP/GaAs(001), is analyzed. 15 refs., 6 figs.« less

The primary mechanism that leads to the suppression of Auger recombination effects in compressively strained quantum wells is found due to the existence and the appropriate positioning of negative-curvature zones in the first valence subbands (zones in k space where the radial curvature of the first valence subband is negative). By studying previous Monte Carlo calculation results, strong correlations between the negative-curvature zones and its adverse effects on Auger recombinations are observed, thereby confirming this finding. Through this understanding, it is inferred that compressive strain is most effective for reduction of Auger recombination effects when the amount of strain is no more than 1.0%. Beyond 1.0%, the gain in device performance with respect to more compressive strain is expected to be greatly diminished.

InGaAsP lasers incorporating strained quantum wells have recently shown superior performance in the 1.3 /spl mu/m band. We report both high-power, low RIN lasers and high-speed, low theshold lasers obtained from strained quantum well material. In conclusion, we have demonstrated high-performance 1.3 /spl mu/m lasers obtained from strained quantum well material. Lasers can be optimized for both analog and digital applications.

The fabrication of long-wavelength optoelectronic devices on GaAs substrates is an attractive method for monolithic integration of optical and electronic devices on a single chip for applications in telecommunications. In this letter we describe our studies of one such scheme using a novel structure for spatially separating a portion of the biaxial compressive stress due to lattice mismatch of the layers from the well layer, and demonstrate its feasibility. High quality pseudomorphic strained InGaAs quantum wells were grown on GaAs substrates by molecular beam epitaxy with a band edge between 1.3 and 1.4 μm at room temperature. Low-temperature photoluminescence spectroscopy as well as polarization-dependent absorption measurements in a waveguide geometry was used to characterize the structures.

Damage introduced from sputtering deposition, electron-beam evaporation, and thermal evaporation were investigated with an InGaAs/GaAs strained quantum well structure. This strained quantum well structure was found to be a more sensitive probe of damage, revealing metallization-induced damage where none was found using comparable lattice-matched quantum wells. The damage was found to vary with deposition method, deposition rates, or even different metal sources used. Noticeable degradation of the photoluminescence of the strained quantum well was observed after a thin layer (∼100 Å) of metal was deposited.

A detailed experimental and theoretical study of the optical transitions in strained quantum wells has been carred out. The quantum wells are grown so that the well region is under biaxial compressive (InvGai As/A1 Gai As system) or under biaxial tensile (GaAs/ InGaAlAs or GaAsP/A1GaAs systems)ltrainY. lfiYs allows the possibility of reversing the light hole-heavy hole ordering. Theoretical studies are based on solving the Kohn-Luttinger Hamiltonian for the hole state after taking account of the strain via a deformation potential formalism. Experimental data were obtained from low-temperature absorption measurements. Emphasis has been given, in particular, to quantum well structures with biaxial tensile strain in the well region. In this structure, by a careful selection of strain, coincidence of light hole (LH) and heavy hole (HH) states has been achieved and this has consequently enhanced absorption coefficient by a factor of about 2. Theoretical studies on the GaAs (well)/InGaAlAs (barrier) and GaAsP/AlGaAs structures confirm this enhancement is due to increase in the oscillator strength due to the merger of the HH and LH excitons and an increase in joint density of states as a result of large in-plane hole masses. This behavior opens up the possibility of artificially enhancing the quantum efficiency of high frequency photodiodes or of fabricating modulator with high on/ off ratio.

Laser emission in HgCdTe in the 2–3.5 μm range

General approach is described to the rates, fluxes and current densities associated with spontaneous radiative and nonradiative Auger recombinations in heterostructure lasers with different types of a quantum-confined active region (quantum wells, quantum wires, and quantum dots). The proper way of defining the spontaneous radiative and Auger recombination coefficients and their dimensionality are discussed. It is shown that only in a quantum dot, true time constants can be introduced for spontaneous radiative and nonradiative Auger recombinations, which are independent of the injection level. Closed-form elegant expressions are presented for the radiative recombination coefficient as an explicit function of temperature and parameters in bulk and quantum-confined structures. These expressions clearly demonstrate inappropriateness of the common practice of deriving the recombination coefficients in low-dimensional heterostructures from the bulk values.

Measuring the turn-on delay of diode lasers provides useful information on carrier recombination dynamics, particularly Auger recombination, essential for their design for high-speed modulation and power-efficient performance. Here we present a rigorous, comprehensive relationship between the time delay and the Auger recombination coefficient. We demonstrate the application of this formulation by extracting this coefficient for AlGaInAs/InP quantum wells incorporated in long-wavelength vertical-cavity surface-emitting lasers.

Interface roughness correlation in CdTe/CdZnTe strained quantum wells

Photoluminescence investigation on growth mode changeover in Ge-rich Si 1− xGe x/Si strained quantum wells

The internal quantum efficiency of (In,Ga)N/GaN quantum wells can surpass 90% for blue-emitting structures at moderate drive current densities but decreases significantly for longer emission wavelengths and at higher excitation rates. This latter effect is known as efficiency "droop" and limits the brightness of light-emitting diodes (LEDs) based on such quantum wells. Several mechanisms have been proposed to explain efficiency droop including Auger recombination, both intrinsic and defect-assisted, carrier escape, and the saturation of localized states. However, it remains unclear which of these mechanisms is most important because it has proven difficult to reconcile theoretical calculations of droop with measurements. Here, we first present experimental photoluminescence measurements extending over three orders of magnitude of excitation for three samples grown at different temperatures that indicate that droop behavior is not dependent on the point defect density in the quantum wells studied. Second, we use an atomistic tight-binding electronic structure model to calculate localization-enhanced radiative and Auger rates and show that both the corresponding carrier density-dependent internal quantum efficiency and the carrier density decay dynamics are in excellent agreement with our experimental measurements. Moreover, we show that point defect density, Auger recombination, and the effect of the polarization field on recombination rates only limit the peak internal quantum efficiency to about 70% in the resonantly excited green-emitting quantum wells studied. This suggests that factors external to the quantum wells, such as carrier injection efficiency and homogeneity, contribute appreciably to the significantly lower peak external quantum efficiency of green LEDs.

GaSb/InGaSb strained-layer quantum wells by MOCVD

This article investigates and improves optical properties of slow light devices. The device structure consists GaAs/AlGaAs [110] strained quantum wells (QWs) based on V-type electromagnetically induced transparency (EIT). In this paper, we use an analytical model in fractional dimension in order to simulate and analysis slow light device. Effects of well width variation have been investigated on exciton oscillator strength (EOS) and fractional dimension parameter. Influences of these parameters alterations have been illustrated in optical properties of slow light system such as slow down factor (SDF) and central energy of the device. Based on obtained results, we can adjust optical variables of slow light system with controlling the well thickness. Using proposed method, we have also estimated the maximum value of SDF about 9×103.

In-plane optical anisotropy was calculated for InGaAs strained quantum wells (QWs) with finite barrier potential on high-index (11n)-oriented GaAs substrates. The mixing effects of the spin–orbit split-off (SO) band were included by using 6 ×6 Hamiltonian based on the Luttinger–Kohn model. Calculated results reveal that optical anisotropy of the narrow QW is strongly dependent on barrier potential height, because the SO band mixing is enhanced by the strong confinement. Substrate off-angle dependence of photoluminescence intensity anisotropy observed in the (11n)A (n = 3, 4, and 5) In0.08Ga0.92As/GaAs strained QWs is well explained by the calculated curve with taking into account of the SO band mixing.