Silicon carbide white light LEDs for solid-state lighting

Abstract

White light emitting diodes (LEDs) have been successfully fabricated for the first time in silicon carbide substrates (4H-SiC) using a novel laser doping technique. The donor-acceptor pair (DAP) recombination mechanism for luminescence has been used to tailor these LEDs. Chromium (Cr), which produces multiple acceptor sites per atom, and selenium which produces multiple donor sites per atom were successfully incorporated into SiC for the first time using laser doping. Aluminum (Al) and nitrogen (N) were also laser-doped into SiC. Green (521-575 nm) and blue (460-498 nm) wavelengths were observed due to radiative recombination transitions between donor-acceptors pairs of N-Cr and N-Al respectively, while a prominent violet (408 nm) wavelength was observed due to transitions from the nitrogen level to the valence band level. The red (698-738 nm) luminescence was mainly due to nitrogen excitons and other defect levels. This RGB combination produced a broadband white light spectrum extending from 380 to 900 nm. The color space tri-stimulus values were X = 0.3322, Y = 0.3320 and Z = 0.3358 as per 1931 CIE (International Commission on Illumination) for 4H-SiC corresponding to a color rendering index of 96.56; the color temperature of 5510 K is very close to average daylight (5500 K).

Metal-assisted chemical etching beyond Si: applications to III–V compounds and wide-bandgap semiconductors

“…49,[164][165][166] The compound exists in several polytypes, two of the most important forms are the 6H and the 4H phases, which have good stability at applicable temperatures and desirable electronic applications. 167 SiC is employed for a range of applications including integrated photonics, 168 radiofrequency devices, 169 visible LEDs, 170 UV photodetectors, 171 and sensors. 172 Due to the wide bandgap, UV illumination to excite electrons to the conduction band is generally required for MacEtch of SiC to proceed.…”