An analysis of Hall mobility in as-grown and annealed n- and p-type modulation-doped GaInNAs/GaAs quantum wells

In this study, we investigate the effect of annealing and nitrogen amount on electronic transport properties in n- and p-type-doped Ga_0.68In_0.32N_yAs_{1 − y}/GaAs quantum well (QW) structures with y = 0%, 0.9%, 1.2%, 1.7%. The samples are thermal annealed at 700°C for 60 and 600 s, and Hall effect measurements have been performed between 10 and 300 K. Drastic decrease is observed in the electron mobility of n-type N-containing samples due to the possible N-induced scattering mechanisms and increasing effect mass of the alloy. The temperature dependence of electron mobility has an almost temperature insensitive characteristic, whereas for p-type samples hole mobility is decreased drastically at T > 120 K. As N concentration is increased, the hole mobility also increased as a reason of decreasing lattice mismatch. Screening effect of N-related alloy scattering over phonon scattering in n-type samples may be the reason of the temperature-insensitive electron mobility. At low temperature regime, hole mobility is higher than electron mobility by a factor of 3 to 4. However, at high temperatures (T > 120 K), the mobility of p-type samples is restricted by the scattering of the optical phonons. Because the valance band discontinuity is smaller compared to the conduction band, thermionic transport of holes from QW to the barrier material, GaAs, also contributes to the mobility at high temperatures that results in a decrease in mobility. The hole mobility results of as-grown samples do not show a systematic behavior, while annealed samples do, depending on N concentration. Thermal annealing does not show a significant improvement of electron mobility.     

Adaptive mixture methods based on Bregman divergences

We investigate adaptive mixture methods that linearly combine outputs of m constituent filters running in parallel to model a desired signal. We use Bregman divergences and obtain certain multiplicative updates to train the linear combination weights under an affine constraint or without any constraints. We use unnormalized relative entropy and relative entropy to define two different Bregman divergences that produce an unnormalized exponentiated gradient update and a normalized exponentiated gradient update on the mixture weights, respectively. We then carry out the mean and the mean-square transient analysis of these adaptive algorithms when they are used to combine outputs of m constituent filters. We illustrate the accuracy of our results and demonstrate the effectiveness of these updates for sparse mixture systems.     

Modified kaolinites‐polyalkyl methacrylate nanocomposites: Exploring relations between solubility parameters and thermal properties for in situ solution polymerization

Poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and their nanocomposites (Kao‐PMMAs and Kao‐PEMAs) with various kaolinite intercalation compounds were prepared in several solution polymerization media in order to examine relations between solubility parameters of polymerization medium including monomer and solvent/solvents and of intercalating agents and thermal properties of the resultant materials. The measurements of X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetry/derivative thermogravimetry, and differential scanning calorimetry were used to characterize these materials. The increase in solubility parameter of polymerization medium improved thermal decomposition temperatures of PEMA and Kao‐PEMAs when it usually induced a decrease in those of PMMA and Kao‐PMMAs and in glass transition temperatures of all materials. These results were also examined in respect of the effects of hydrogen bonding and dispersion components of solubility parameters of intercalating agents on the thermal properties of these materials. POLYM. COMPOS., 37:2333–2341, 2016. © 2015 Society of Plastics Engineers