Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates

Abstract

Due to the absorption of opaque Si substrates, the luminous efficiency of GaN-based light-emitting diodes (LEDs) on Si substrates is not high. So, in this work, we insert AlN/GaN distributed Bragg reflectors (DBRs) to improve the light output of GaN-based LEDs on Si (111) substrates grown via metal organic chemical vapor deposition (MOCVD). In order to obtain the highest reflectivity of the AlN/GaN DBR stop band, the growth parameters of AlN/GaN DBRs are optimized, including the growth temperature, the V/III ratio and the growth pressure. As a consequence, the interfaces of the optimal 9-pair AlN/GaN DBRs become abrupt, and the reflectivity of the DBR stop band is as high as 85.2%, near to the calculated value (92.5%). Finally, crack-free GaN-based LEDs with 5-pair AlN/GaN DBRs are grown on Si (111) substrates. The light output of the DBR-based LED is evidently enhanced by 41.8% at the injection current of 350 mA, compared with the conventional DBR-based LED without DBRs. These results pave the way for the luminous efficiency improvement of future green and red GaN-based LEDs grown on Si substrates.

Improved Optical Efficiency of 850-nm Infrared Light-Emitting Diode with Reflective Transparent Structure

“…The results of the light-emitting paths in Figure 4 verified that the use of transparent and reflective layers was a more attractive method for improving the light extraction efficiency of the IR-LED chip, because the light-emitting path in the LED chip was limited by the intrinsic problems of an insignificant sideway emission area and the low reflectivity of the specific wavelength [ 15 ]. The results in Figure 3 and Figure 4 demonstrate that the light extraction efficiency of IR-LEDs can be improved using either the transparent epitaxial layer or the reflective bonding layer.…”

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

“…• the ohmic losses are negligible in the semiconductor chip; • the mirror presence (e.g., metallic layer or distributed Bragg reflector [35]) can enlarge the efficiency by about 59%; • a large magnitude of emitted energy may result in a negative energy balance inside the semiconductor chip; • due to high doping level, the contact losses at metal-semiconductor contacts are small or even disappear in the case of degenerate semiconductors;…”

Determination of scattering mechanisms in AlInGaN/GaN heterostructures grown on sapphire substrate

“…The GaN-based devices are applied intensively in high power electronic and optoelectronic technologies, such as high electron mobility transistors (HEMTs) [1][2][3], light-emitting diodes (LEDs) [4][5][6][7], and laser diodes (LD) [8][9][10], and UV detectors [11,12] owing to its wide bandgap, high mobility, high electron saturation velocity, and high thermal conductivity [13].…”