Browsing by Subject "External electric field"
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Item Open Access Electric field dependence of radiative recombination lifetimes in polar InGaN/GaN quantum heterostructures(IEEE, 2009) Sarı, Emre; Nizamoğlu, Sedat; Lee I.-H.; Baek J.-H.; Demir, Hilmi VolkanWe report on external electric field dependence of recombination lifetimes in polar InGaN/GaN quantum heterostructures. In our study, we apply external electric fields one order of magnitude less than and in opposite direction to the polarization-induced electrostatic fields inside the well layers. Under the increasing external electric field, we observe a decrease in carrier lifetimes (τ) and radiative recombination lifetimes (τr), latter showing a weaker dependence. Our results on τr show an agreement with our transfer matrix method based simulation results and demonstrate Fermi's golden rule in polar InGaN/GaN quantum heterostructures dependent on electric field. For our study, we grew 5 pairs of 2.5 nm thick In0.15Ga 0.85N quantum well and 7.5 nm thick GaN barrier layers in a p-i-n diode architecture using metal-organic chemical vapor deposition (MOCVD) on a c-plane sapphire substrate. Devices with 300 μm × 300 μm mesa size were fabricated using standard photolithography, reactive ion etching and metallization steps. We used indium-tin oxide (ITO) based semi-transparent contacts in top (p-GaN) layer for uniform application of electric field across the well layers. The fabricated devices were diced and mounted on a TO-can for compact testing. © 2009 IEEE.Item Open Access Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields(American Institute of Physics, 2009-05-29) Sari, E.; Nizamoglu, S.; Lee, I. H.; Baek, J. H.; Demir, Hilmi VolkanElectric field dependent photoluminescence decay kinetics and its radiative component are studied in polar InGaN/GaN quantum heterostructures at low fields. Under externally applied electric field lower than polarization fields, spectrally and time resolved photoluminescence measurements are taken to retrieve internal quantum efficiencies and carrier lifetimes as a function of the applied field. Subsequently, relative behavior of radiative recombination lifetimes is obtained in response to the applied field. In these characterizations of polar InGaN/GaN structures, we observe that both the carrier lifetime and the radiative recombination lifetime decrease with increasing external electric field, with the radiative component exhibiting weaker field dependence.Item Open Access Electric field effects on optical properties of semiconductor nanorods(2009-05) Gurinovich L. I.; Lutich, A. A.; Stupak, A. P.; Prislopskii, S. Va.; Artemyev, M. V.; Rusakov, E. K.; Demir, Hilmi VolkanWe studied electric field effects on optical properties of CdSe/ZnS nanorods integrated in thin films sandwiched between transparent electrodes. It was demonstrated that P-polarized component of the photoluminescence of CdSelZnS nanorods is quenched stronger by external electric field than the S-polarized component. Quantum dots are more sensitive to external electric field than the nanorods. A mechanism of external electric field influence on the luminescence spectrum of semiconductor nanorods is discussed.Item Open Access Liquid bulk rotation induced by electric field at free surface(American Institute of Physics Inc., 2015) Saghaei, T.; Moradi, A.-R.; Shirsavar, R.; Habibi, M.In this paper, we induce rotation in a bulk of polar liquid with one free surface, by applying external crossed electric fields. We show that the induced rotation is due to the imposed stresses at the free surface of the liquid. A simple theoretical model was developed based on solving the Navier-Stokes equation that enables us to calculate the average induced stress in the liquid bulk, using experimental measurements of the angular velocity of the liquid. Our results indicate that the induced stresses and the angular velocities of the rotating liquid are independent from the electrical conductivity of the liquid. However, the induced stresses linearly depend on the external electric field and the applied electric voltage for passing the electric current through the bulk. Both experimental results and the theoretical model show that the angular velocity, linearly changes with depth. © 2015 AIP Publishing LLC.