Expanding horizons for nitride devices & materials

Wurtzite III–Nitride Distributed Bragg Reflectors on Si(100) Substrates

“…Recent work has shown that employing a Si(100) substrate that is offcut by 4 to 5 deg will introduce an asymmetric constraint that allows for deposition of single-crystal wurtzite GaN. 7,8) Deposition of GaN on Si is plagued by a large difference in thermal expansion between the film and the substrate that generates a high density of cracks when the structure is cooled from growth to room temperature. On Si(111), several groups employed a superlattice (SL) or graded AlGaN layer inserted near the AlN buffer to introduce a compressive stress during growth that compensates for the large tensile thermal stress.…”

“…11,12) The use of a offcut Si(100) substrate further exacerbates this issue by introducing a large number of stepedges which disturbs the lattice ordering during the initial stages of III-nitride growth. 13) Despite these impediments, III-nitride light emitting diodes and high electron mobility transistors have been recently demonstrated on Si(100) substrates; 7,8) however, there have been no reports of distributed Bragg reflectors (DBRs) on Si(100). The ability to create III-nitride DBRs on Si(100) would open the possibility for improved design of devices for the generation, detection and propagation of UV and visible light including laser diodes, detectors, and waveguides.…”