Optical transmission properties of C-shaped subwavelength waveguides on silicon

Optical properties of C-shaped subwavelength waveguides in metallic (silver) films on silicon substrates are studied in the range of 0.6-6 mu m. Power throughput and resonant wavelengths of several transmission modes are studied by varying the waveguide length (or metal thickness). Among three types of transmission modes, the fundamental order of the Fabry-Perot-type mode was shown to attain remarkably high power throughputs (as high as 12). With optimized design of the aperture, the resonant wavelength of this mode occurs in the 1-2 mu m wavelength range, suggesting that such apertures can be utilized to achieve plasmonic-enhanced silicon photonic devices at telecommunication wavelengths

Studies of minority carrier diffusion length increase in p-type ZnO : Sb

Minority electron diffusion length was measured in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. A thermally induced increase of electron diffusion length was determined to have an activation energy of 184 +/- 10 meV. Irradiation with a low energy (5 kV) electron beam also resulted in an increase of diffusion length with a similar activation energy (219 +/- 8 meV). Both phenomena are suggested to involve a Sb-Zn-2V(Zn) acceptor complex. Saturation and relaxation dynamics of minority carrier diffusion length are explored. Details of a possible mechanism for diffusion length increase are presented

Electron irradiation-induced increase of minority carrier diffusion length, mobility, and lifetime in Mg-doped AlN/AlGaN short period superlattice

Minority carrier diffusion length in a p-type Mg-doped AlN/Al(0.08)Ga(0.92)N short period superlattice was shown to undergo a multifold and persistent (for at least 1 week) increase under continuous irradiation by low-energy beam of a scanning electron microscope. Since neither the diffusion length itself nor the rate of its increase exhibited any measurable temperature dependence, it is concluded that this phenomenon is attributable to the increase in mobility of minority electrons in the two-dimensional electron gas, which in turn is limited by defect scattering. Cathodoluminescence spectroscopy revealed similar to 40% growth of carrier lifetime under irradiation with an activation energy of 240 meV

Doping level dependence of electron irradiation-induced minority carrier diffusion length increase in Mg-doped GaN

The electron irradiation-induced increase of minority carrier diffusion length was studied as a function of hole concentration in Mg-doped GaN. Variable-temperature electron beam induced current measurements yielded activation energies of 264, 254, 171, and 144 meV for samples with hole concentrations of 2x10(16), 9x10(16), 3x10(18), and 7x10(18) cm(-3), respectively. This carrier concentration dependence of the activation energy for the effects of electron irradiation was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in the irradiation-induced diffusion length increase

Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN

Electron-irradiation increase of nonequilibrium carrier lifetime was studied as a function of hole concentration in Mg-doped GaN. Temperature-dependent cathodoluminescence (CL) studies yielded activation energies of 344, 326, 237, and 197 meV for samples with hole concentrations of 2x10(16), 9x10(16), 3x10(18), and 7x10(18) cm(-3), respectively. The systematic decay of activation energy with carrier concentration was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in irradiation-induced lifetime changes

Influence of electron injection on the photoresponse of ZnO homojunction diodes

Forward bias electron injection into the p side of a p-n homojunction was shown to result in an improved response of the ZnO photodiodes. Injection of about 25 C of charge yielded a nearly 2.5-fold increase of photocurrent at 350 nm. This improvement was correlated with the increase of the diffusion length of minority electrons in p-type ZnO:Sb as determined by electron beam induced current measurements. It is suggested that the increase of the diffusion length is related to the carrier trapping on nonionized acceptor levels

Influence of electron injection on the temporal response of ZnO homojunction photodiodes

The effects of solid-state electron injection on the peak amplitude and decay time of photosignal in a ZnO-based homojunction UV photodiode were studied using temporal photoresponse measurements under femtosecond pulses of 355 nm radiation. The injection of about 50 C of charge, carried out by applying forward bias to the junction, resulted in a nearly twofold increase of the peak photoresponse and a corresponding increase of the decay constant. Both observations are shown to be a consequence of electron trapping. The long-term stability of the induced changes is also discussed

Carrier concentration dependence of acceptor activation energy in p-type ZnO

The characteristics of an acceptor level in Sb-doped, p-type ZnO were studied using cathodoluminescence (CL) spectroscopy as a function of hole concentration. Variable-temperature CL measurements allowed us to estimate the activation energy of an Sb-related acceptor from temperature-induced decay of CL intensity. The values of activation energy of about 212 +/- 28, 175 +/- 20, 158 +/- 22, and 135 +/- 15 meV were obtained for samples with carrier concentrations of 1.3x10(17), 6.0x10(17), 8.2x10(17), and 1.3x10(18) cm(-3), respectively. The involvement of acceptor levels is supported by the temperature-dependent hole concentration measurements. The possible origins of the strong temperature dependence are discussed