Growth of strain-relaxed InGaN on micrometer-sized patterned compliant GaN pseudo-substrates
Shubhra S. Pasayat, Chirag Gupta, Matthew S. Wong, Yifan Wang, Shuji Nakamura, Steven P. DenBaars, S. Keller, Umesh K. Mishra
Abstract
The compliant behavior of high fill-factor 10 × 10 μm2 square patterned 60–140 nm thick GaN-on-porous-GaN tiles was demonstrated by utilizing porous GaN as a semi-flexible underlayer. High resolution x-ray diffraction measurements showed a larger a-lattice constant of InGaN layers deposited on these patterned GaN-on-porous GaN pseudo-substrates in comparison to those deposited on co-loaded planar GaN-on-sapphire templates. Additionally, InGaN based light emitting diode (LED) structures deposited on these GaN pseudo-substrates exhibited room temperature electroluminescence at 547 nm compared to 506 nm for the LED structures grown on co-loaded planar GaN on sapphire templates, corresponding to a redshift of around 40 nm. The longer emission wavelength was associated with the higher indium incorporation into the InGaN quantum wells deposited on the compliant GaN pseudo-substrates, owing to a reduced lattice mismatch between the quantum well and the n-InGaN base layers grown on the compliant pseudo-substrates, due to the composition pulling effect.