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Öğe Analytic modeling of temperature dependence of 2D carrier mobility in as-grown and annealed GaInNAs/GaAs quantum well structures(Iop Publishing Ltd, 2014) Donmez, O.; Sarcan, F.; Lisesivdin, S. B.; Vaughan, M. P.; Erol, A.; Gunes, M.; Arikan, M. C.Temperature and nitrogen dependence of 2D carrier mobility in as-grown and annealed Ga1-xInxNyAs1-y/GaAs quantum well (QW) structures (x = 0.32; y = 0, 0.009, and 0.012) are investigated. An analytical model that accounts for the most prominent scattering mechanisms is used to explain the characteristic of temperature dependence of the carrier mobility. An expression for alloy scattering-limited mobility in N-related alloys is developed to explain the behavior of hole mobility for N-containing p-type samples. Analytical modeling of temperature dependence of the electron mobility indicates that N-related alloy scattering and interface roughness scattering are the dominant mechanism at the entire temperature range of interest. The temperature insensitivity of the electron mobility is explained in terms of the overriding effect of N-related alloy scattering and high 2D electron density. A deviation between theoretical and experimental electron mobility at low temperatures is observed not to have any dependency on N concentration. We, therefore, suggest that C-NM interaction parameter of the band anti-crossing (BAC) model must be defined as temperature dependent in order to explain the observed low temperature characteristics of electron mobility. The hole mobility is mainly restricted by interface roughness and alloy scatterings at temperatures lower than 100 K, whilst high temperature hole mobility is drastically affected from optical phonon scattering. Moreover, the hole mobility at high temperatures exhibits an N-independent characteristic and hole density starts to increase at temperatures above 70 K, which is explained using the concept of parallel conduction. Extraction of the hole density in each transport channel (QW and barrier) by using a simple parallel conduction extraction method (SPCEM) shows that, in p-type samples, low temperature hole mobility takes place in quantum well, while as temperature increases barrier channel also contribute to the hole mobility and becomes dominant at high temperatures. The experimental and calculated Hall mobility results reveal that thermal annealing has decreased interface roughness and alloy scatterings.Öğe Effect of doping on transport properties of InSb epilayers grown by MOCVD and MBE(Elsevier, 2024) Gunes, M.; Aydin, M.; Donmez, O.; Gumus, C.; Erol, A.; Marroquin, J. F. R.; Felix, J. F.Temperature-dependent carrier transport properties of two InSb epilayers grown on GaAs substrates by Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) are investigated. The InSb epilayer grown by MBE was undoped, but the undoped InSb epilayer grown by MOCVD was grown on a thin Zndoped InSb layer. Hall Effect results showed that the Hall coefficients (RH) for InSb grown by MBE and MOCVD are negative in temperature ranges 4.2 K-300 K and 200 K-300 K, respectively. However, for the InSb sample grown by MOCVD, RH switches from a positive to a negative value for temperatures above similar to 180 K, which could be due to the capture electrons generated from dislocation between InSb and GaAs by Zn atoms. The electron mobilities of InSb grown by MBE and MOCVD were 38,247 and 51,704 cm(2)/Vs, respectively. Low-temperature magnetoresistance measurements showed clear Shubnikov-de-Haas oscillations (SdH) in MBE InSb; however, no SdH oscillations were observed in MOCVD InSb samples.Öğe Influence of nitrogen on hole effective mass and hole mobility in p-type modulation doped GaInNAs/GaAs quantum well structures(Amer Inst Physics, 2013) Sarcan, F.; Donmez, O.; Erol, A.; Gunes, M.; Arikan, M. C.; Puustinen, J.; Guina, M.Nitrogen dependence of hole effective mass and hole mobility in p-type modulation doped Ga0.68In0.32NyAs1-y/GaAs quantum well structures with y = 0, 0.009, 0.012, 0.017 are investigated using magnetotransport and Hall effect measurements. Observed N-dependent reduction of the hole effective mass is explained by stronger confinement of holes. Hole effective mass is also found to have hole density dependence due to the strain-induced valance band non-parabolicity. A tendency to decrease in hole effective mass upon annealing can be attributed to the reduction of well width and/or decrease in hole density. A significant improvement in low temperature hole mobility is observed after annealing. (C) 2013 AIP Publishing LLC.Öğe Optical properties of GaAs1-xBix/GaAs quantum well structures grown by molecular beam epitaxy on (100) and (311)B GaAs substrates(Iop Publishing Ltd, 2018) Gunes, M.; Ukelge, M. O.; Donmez, O.; Erol, A.; Gumus, C.; Alghamdi, H.; Galeti, H. V. A.In this work, the electronic bandstructure of GaAs1-xBix/GaAs single quantum well (QW) samples grown by molecular beam epitaxy is investigated by photomodulated reflectance (PR) measurements as a function of Bi content (0.0065 <= x <= 0.0215) and substrate orientation. The Bi composition is determined via simulation of high-resolution x-ray diffraction measurement and is found to be maximized in the 2.15%Bi and 2.1%Bi samples grown on (100) and (311)B GaAs substrates. However, the simulations indicate that the Bi composition is not only limited in the GaAsBi QW layer but extends out of the GaAsBi QW towards the GaAs barrier and forms a GaAsBi epilayer. PR spectra are fitted with the third derivative function form (TDFF) to identify the optical transition energies. We analyze the TDFF results by considering strain-induced modification on the conduction band (CB) and splitting of the valence band (VB) due to its interaction with the localized Bi level and VB interaction. The PR measurements confirm the existence of a GaAsBi epilayer via observed optical transitions that belong to GaAsBi layers with various Bi compositions. It is found that both Bi composition and substrate orientation have strong effects on the PR signal. Comparison between TDFF and calculated optical transition energies provides a bandgap reduction of 92 meV/%Bi and 36 meV/%Bi and an interaction strength of the isolated Bi atoms with host GaAs valence band (C-BiM) of 1.7 eV and 0.9 eV for (100) and (311)B GaAs substrates, respectively.Öğe The effect of strain and spatial Bi distribution on the band alignment of GaAsBi single quantum well structure(Elsevier, 2021) Gunes, M.; Donmez, O.; Gumus, C.; Erol, A.; Alghamdi, H.; Alhassan, S.; Alhassni, A.The band line-up and band offset calculations of GaAs0.978Bi0.022/GaAs single quantum well with spatial changes of Bi composition were reported. The spatial Bi profile and a certain amount of the Bi composition in the barrier layer were determined by HR-XRD measurements. Virtual Crystal Approximation and Valence Band Anti-Crossing models were used including strain effects to obtain conduction and valence band edge shifts with Bi incorporation. Photoluminescence (PL) measurements were performed at a low temperature of 8 K as a function of excitation intensity. The PL spectra have shown asymmetric line shapes, which were fitted with different Gaussian functions. Comparing experimental PL results with calculated band edge energies, it was found that optical transition is a type I under low intensity excitation while the optical transition is switched from type I to type II due to the spatial changes in Bi concentrations. The band offsets Delta E-c/Delta E-v were also determined.
