The characterizations of n-type doped GaN, p-type doped GaN and n-type doped In0.2Ga0.8N Schottky metal-semiconductor-metal (MSM) photodetectors were reported. The epilayers were grown on sapphire by metalorganic chemical vapor deposition (MOVCD). Schottky contacts were fabricated using Au, Ti, Ni and Pt metals. The dark and illuminated current–voltage characteristics of GaN and InGaN MSM photodetectors with different Schottky metals were studied. The n-GaN MSM photodetectors with Au Schottky contacts showed better responsivity than those with other metals and they were also better than Au/p-GaN and Ti/n-In0.2Ga0.8N MSMs. The effects of the pitch width between the interdigitate fingers and the thickness of Schottky metals on the characteristics of photocurrents were also studied.

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Silicon oxide (SiO x ) and silicon nitride (SiN x ) thin films have been deposited onto flexible polycarbonate (PC) substrates using plasma-enhanced (PE)CVD for transparent barrier applications. Comparing the internal stress, optical transparency, surface roughness, and impermeability results, a multilayer composed of parylene/SiO x /SiN x ...parylene/SiO x /SiN x (PON...PON) is deposited on PC substrates and the optimum thicknesses of the SiN x , SiO x , and parylene layers is determined. Under optimum conditions, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of SiO x (50 nm)/SiN x (50 nm) barrier coatings on PC at 80°C decreases to values near 0.01 g m -2 per day and 0.1 cm 3 m -2 per day, respectively. To further reduce the WVTR and OTR values, parylene layers are used as a smoothing, defect-decoupling, and protective medium in the multilayer. It has been found that organic light-emitting diodes capped with double PON layers show no dark spots and exhibit better emissions than single PON layers after 100 h at 25°C, and 40 % relative humidity.

Tin doped indium oxide (In 2 O 3 :Sn) or indium tin oxide (ITO) thin films have been successfully deposited by the low cost spray-pyrolysis method. Low sheet resistance and high mobility films were obtained when the films were deposited at the substrate temperature of 793 K. The direct optical bandgaps for the films deposited at 793 (a) and 753 K (b) were found to be 3.46 and 3.40 eV, respectively. Similarly, the indirect bandgaps for a-and b-type films were found to be 3.0 and 2.75 eV, respectively. The Burstein-Moss shift was observed in the films. The refractive index (n) and extinction coefficient (k) were found to be in the range of 2.1 to 1.1 and 0.6 to 0.01, respectively. The various scattering mechanisms such as lattice, ionized impurity, neutral impurity, grain boundary and alloy scattering due to variation of theoretical mobilities with temperature are discussed, in order to compare experimental results. In the lattice scattering mechanism, the quantum size effect phenomena were employed to estimate the energy dilation (E I ). The a-type films exhibited SnO 2 as secondary phase whereas b-type films showed single phase In 2 O 3 :Sn with high sheet resistance. The lattice constants were found to be 10.16 and 10.09 Å for a-and b-type films, respectively.

InGaN ( 3 nm ) ∕ GaN ( 5 nm ) three period multiquantum green-light-emitting diodes (LEDs) grown by the metalorganic chemical vapor deposition technique have been studied using high-resolution transmission electron microscopy (HRTEM), double crystal high resolution x-ray diffraction (HRXRD) and low temperature photoluminescence. HRTEM analysis showed that the defect density gradually decreased in the growth direction with increasing thickness. Self-assembled quantum dot-like structures in the wells and black lumps between the well and barrier due to In segregation and strain contrast were observed, respectively. The HRXRD spectrum of the green LED structure was simulated using the kinematical theory method to obtain the composition and thickness of the well and barrier. The quantum-well (QW) green emission peak 2.557eV at 10K showed “S” shaped shift like a red–blue–red shift with variation of the temperature in the photoluminescence spectra due to potential fluctuations caused by inhomogeneous alloy distribution in the wells. The activation energy of 49meV obtained from the QW green emission line indicated deepening of the localization of the carriers.