h i g h l i g h t s < Multi-year, international efforts for studying aerosol and climate impacts across Southeast Asia. < Aerosol and cloud properties measured from both ground-and satellite-based platforms. < Investigation of aerosolecloud interactions and planning for future experiments.
We report the direct observation of transferred-electron effect in unintentionally doped GaN epilayers grown by metalorganic chemical vapor deposition. The negative differential resistivity (NDR) was observed from the current-electric field characteristics in GaN using a metal-semiconductor-metal (M-S-M) system. The threshold field for the onset of NDR was independent of the spacing of M-S-M fingers, and was measured to be 1.91×105 V/cm for GaN with an n-type carrier concentration of 1014 cm−3. This value is very close to the value obtained from theoretical simulation. This observation is an experimental evidence of transferred-electron effects in GaN, which is important in understanding GaN energy band structure and in the application of Gunn-effect devices using GaN materials.
The observation of optical quenching of photoconductivity in GaN photoconductors at room temperature is reported on. Three prominent quenching bands were found at Ev+1.44, 1.58, and 2.20 eV, respectively. These levels are related to three hole traps in GaN materials based on a hole trap model to interpret the quenching mechanism. The responsivity was reduced about 12% with an additional He–Ne laser shining on the photoconductor.
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