The polarity and mechanism of terahertz radiation from native n-type InN excited by femtosecond optical pulses are investigated. The optical properties, electron concentrations, and crystalline quality are characterized by photoluminescence and Raman scattering spectra. The electron concentrations are estimated to be between 0:35 Â 10 19 and 3:87 Â 10 19 cm À3 . The polarity of terahertz radiation field from the samples with higher electron concentrations is opposite to that from p-InAs, indicating that the dominant radiation mechanism is the drift current. However, the samples with lower electron concentrations show the same polarity as p-InAs. Under this condition, the radiation mechanism is dominated by the photo-Dember effect.

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The features of eight-period In0.2Ga0.8N/GaN quantum wells (QWs) with silicon (Si) doping in the first two to five quantum barriers (QBs) in the growth sequence of blue light-emitting diodes (LEDs) are explored. Epilayers of QWs’ structures are grown on 20 pairs of In0.02Ga0.98N/GaN superlattice acting as strain relief layers (SRLs) on patterned sapphire substrates (PSSs) by a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. Temperature-dependent photoluminescence (PL) spectra, current versus voltage (I-V) curves, light output power versus injection current (L-I) curves, and images of high-resolution transmission electron microscopy (HRTEM) of epilayers are measured. The consequences show that QWs with four Si-doped QBs have larger carrier localization energy (41 meV), lower turn-on (3.27 V) and breakdown (− 6.77 V) voltages, and higher output power of light of blue LEDs at higher injection current than other samples. Low barrier height of QBs in a four-Si-doped QB sample results in soft confinement potential of QWs and lower turn-on and breakdown voltages of the diode. HRTEM images give the evidence that this sample has relatively diffusive interfaces of QWs. Uniform spread of carriers among eight QWs and superior localization of carriers in each well are responsible for the enhancement of light output power, in particular, for high injection current in the four-Si-doped QB sample. The results demonstrate that four QBs of eight In0.2Ga0.8N/GaN QWs with Si doping not only reduce the quantum-confined Stark effect (QCSE) but also improve the distribution and localization of carriers in QWs for better optical performance of blue LEDs.

This study is a preliminary evaluation of the potential for using deep sea water and solar energy (or hot-spring water) source to economic benefits of thermoelectric power in Taiwan. we investigated that solar energy and high temperature spring water was replaced to the surface sea water to increase the temperature difference (70~85oC). Use of innovative, green, renewable energy resource  enables the  City (Town) to reduce its demand for electricity by approximately 0.5 million kilowatt hours annually (reduction  of up to 65 per cent compared to conventional power system, reduced electricity demand and consequently lower emissions of air pollutants and greenhouse gases.)  We propose an energy-balanced mathematical model considering thermal sources and heat effects to precisely evaluate the capacity of thermoelectric power systems. The research is low temperature of the use the deep ocean water establishes  thermoelectric power system, applies the building already some power system in the substitution, not can only enrich DSW the multi-dimensional use, can gain the energy conservation to reduce the carbon essence benefit.