Blue-Green Light-Emitting Diodes and Violet Laser Diodes

Abstract

Short-wavelength-emitting devices, such as blue laser diodes (LDs) and light-emitting diodes (LEDs), are currently sought for a number of applications, including full-color electroluminescent displays, laser printers, read-write laser sources for high-density information storage on magnetic and optical media, and sources for undersea optical communications. For these purposes, II–VI materials such as ZnSe and SiC, and III–V-nitride semiconductors such as GaN have been investigated intensively for a long time. However it was impossible to obtain high-brightness (over 1 cd) blue LEDs and reliable LDs. Much progress has been achieved recently on green LEDs and LDs using II–VI-based materials. The short lifetimes prevent II–VI-based devices from commercialization at present. The short lifetime of these II-VI-based devices may be caused by the crystal defects at a density of 103/cm2 because one crystal defect would cause the propagation of other defects leading to failure of the devices. Another wide-bandgap material for blue LEDs is SiC. The brightness of SiC blue LEDs is only between 10 mcd and 20 mcd because of the indirect bandgap of this material.On green LEDs, the external quantum efficiency of conventional, green GaP LEDs is only 0.1% due to the indirect bandgap of this material. The peak wavelength is 555 nm (yellowish green). As another material for green emission devices, AlInGaP has been used. The present performance of green AlInGaP LEDs is an emission wavelength of 570 nm (yellowish green) and maximum external quantum efficiency of 1%.

Fabrication of GaN mesa structures

“…Ti, Ti/Al and TiN [7] [8] [9] [10] were utilized for n-GaN. TiN, Au, Au/Mg [8] , Cr/Au [11] and Ni/Au [12] were used for p-GaN. We investigated Ni-based contacts, since Ni can be used as a mask for GaN plasma etching [13], and as a Schottky barrier to n-GaN [14].…”

Time-resolved photoluminescence studies of InGaN/GaN multiple quantum wells

“…For instance, on thick 3-dimensional layers grown with a nominal 12% In composition, Harris et al [4] reported energy-dependent recombination lifetimes. This suggested evidence of extrinsic localization effects, which were later confirmed by independent groups [1] [5]. These effects arise from uncontrolled fluctuations of the alloy composition.…”

“…[1] and references therein). Using the same basic design, but multiple quantum wells (MQWs) stacks in the active region, room temperature operations of laser diodes (LDs) working under pulsed operation conditions have also been demonstrated [2] [3].…”

Density Functional Calculations of Small Anionic Clusters of Group III Nitrides.

“…Recent experimental 18,19 and theoretical 20,22 studies performed on anionic dimers of Al 2 P 2 and Ga 2 P 2 and our previous work on In 2 As 2 31 revealed that the lowest-energy isomer for the anion has a butterfly configuration. In this work, we have computed this structure for all anionic nitride dimers.…”

“…They also have multiple applications as microelectronic elements in hightemperature and high-power electronic devices. 2 Representing a link between the isolated molecular world and the solid state, the study of these clusters with different sizes has drawn increasing attention during the last few years; this attention was mainly focused on Al x N y . [3][4][5][6][7][8][9][10][11][12] A few studies were also carried out on Ga x N y and In x N y .…”