High-power UV InGaN/AlGaN double-heterostructure LEDs

High Al-Content AlInGaN Devices for Next Generation Electronic and Optoelectronic Applications

“…Recently it has been reported by several groups [57][58][59] that the addition of a small amount of indium could lead to an enhancement in PL emission efficiency. Mukai et al [57] demonstrated an GaN:In UV LED with an indium content of around 2% and optical power output as high as 5 mW.…”

“…Mukai et al [57] demonstrated an GaN:In UV LED with an indium content of around 2% and optical power output as high as 5 mW. A series of GaN:In samples (0.2 mm thick on 1 mm GaN epilayers) were grown in which the indium fraction was increased from 0 to approximately 4% as determined by x-ray and RBS.…”

“…At the expense of a shift of emission peak toward longer wavelengths (~380 nm), we attained an increase of more than one order of magnitude in integrated light intensity. Two explanations have been offered to explain the observed enhancement in light emission: carrier localization due to indium incorporation [57] or the suppression of non-radiative recombination defects in the presence of indium [58]. Discussions of these mechanisms are presented in another chapter.…”

“…There has been much empirical observation and speculation that the presence of indium in GaInN ternary layers seems to preserve excited carriers from recombining at non-radiative centers [64]. Mukai et al [57] reported, in the development of ultra-violet LEDs, a rapid reduction of optical efficiency as the In content in the GaInN active region decreased below a certain value. The implication is that the carrier-localization effect [64], possibly due to the presence of a compositional fluctuation of indium, could make AlGaInN an alternative (to GaN or AlGaN) as a short-wavelength (l<360nm) lightemitting medium.…”

“…al. [71] have achieved an impressive 5 mW output at 371 nm from an InGaN/AlGaN DH LED with very low levels of indium (In) in the active region. That LED was reported to have up to 7.5% external quantum efficiency but the efficiency dropped by more than an order of magnitude as the emission wavelength shifted to 368 nm with the total elimination of In from the active region.…”