600 research outputs found
Squares of positive -forms
We show that if is a positive -form then so is . We
also prove that this is no longer true for forms of higher degree
Carrier lifetimes in green emitting InGaN/GaN disksâinânanowire and characteristics of green light emitting diodes
Improvement in the internal quantum efficiency (IQE) of InGaN/GaN disksâinânanowires by surface passivation is demonstrated. The highest IQE achieved through surface passivation for green emitting (λ=540 nm) InGaN/GaN disksâinânanowires is âŒ53%. Radiative and nonradiative carrier lifetimes are calculated for asâgrown and surface passivated green emitting disksâinânanowires. Passivated green sample exhibits a room temperature radiative lifetime of âŒ748 ps, which is much smaller than that of equivalent quantum wells. Electroluminescence measurements on passivated green light emitting diodes containing InGaN disks demonstrate no roll over or efficiency droop up to 375 A/cm 2 , and exhibit a blueâshift of 7 nm in peak wavelength. An enhancement in the light output due to surface passivation is observable in the relative external quantum efficiency of the surface passivated devices as compared with the asâgrown samples. (© 2013 WILEYâVCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98222/1/812_ftp.pd
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