Stress Distribution in GaN Films grown on Patterned Si (111) Substrates and Its Effect on LED Performance

Abstract

Crack free GaN films were grown on 1200×1200 𝜇m 2 patterned Si (111) substrates and 36 light emitting diodes (LEDs) were fabricated in each pattern unit. Spatial distribution of the tensile stress in the pattern units and its influence on the LED performance are studied by micro-Raman and electroluminescence (EL). The Raman shift of the GaN 𝐸2 mode shows that the tensile stress is the maximum at the center, partially relaxed at the edge, and further relaxed at the corner. With the stress relaxation, the EL wavelength has a significant blue shift and the luminous intensity shows a great enhancement.

Influences of stress on the properties of GaN/InGaN multiple quantum well LEDs grown on Si (111) substrates

“…Meanwhile, due to the low cost and large scale, Si substrates have been extensively studied for the growth of GaN-based materials, but LEDs on Si substrates simultaneously face more challenges. [6,7] One difficulty is the stress control on the un-doped GaN materials and n-doped GaN prior to the MQWs. InGaN or InGaN/GaN superlattice prestrain layer has been extensively investigated on MQWs/LED on sapphires, [8][9][10][11][12][13][14][15][16] and it is reported that there were many functions with these layers such as relieving strain in the upper MQWs and weakening QCSE, [8,10,[14][15][16] improving current spreading, [8,9] having a more uniform indium composition in the QWs, [13] reducing the density of V-pits in MQWs, [15,16] and enhancing the internal quantum efficiencies.…”

Temperature-dependent electroluminescence from InGaN/GaN green light-emitting diodes on silicon with different quantum-well structures

“…The green quantum wells (QWs) have higher In-components with more serious piezoelectric polarization effect compared with blue QWs, which increases the band tilt of QWs. That affects carrier distribution, and determines the luminous efficiency of QWs [7]. In addition, it was found that several peaks appeared in the emission spectrum of multiple quantum wells (MQWs) and varied with the change of current density [8,9], from which it was considered that multiple peaks were emitted from different QWs.…”

GaN hexagonal pyramids formed by a photo-assisted chemical etching method

“…[17,18] In addition, the strain distribution along the axial direction of GaN pyramids is quite non-uniform and thus leads to the different optical emissions within the crystal, which strongly affects the performance stability of GaNbased optoelectronic devices. [19,20] Also, the existing lithogra-phy is both complicated and costly. Therefore, it is definitely required to search for another effective method to synthesize GaN pyramids with improved crystal quality for the highperformance GaN nanodevices.…”