GaInN/GaN heterostructures in the cubic lattice variant have the potential to overcome the limitations of wurtzite structures as commonly used for light emitting and laser diodes. Wurtzite GaInN   0001 , suffers from large internal polarization fields, which force design compromises towards ultra-narrow quantum wells and reduced recombination volume and efficiency, particularly in the green, yellow, and red visible spectral regions. Cubic GaInN microstripes on micropatterned Si   001 , with {111} V-grooves oriented along Si 01 1 , offer a system free of internal polarization fields, wider quantum wells, and a smaller bandgap energy. We prepared 6 and 9 nm Ga 1-x In x N/GaN single quantum well structures and find the emission spectrum to be dominated by the recombination in the cubic wells. The peak wavelength ranges from 520 to 570 nm with a

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We model and optimize various light emitting diode structures under bias voltage to maximize emission efficiency with particular respect to piezoelectric polarization. We compare polar and non-polar structures, namely, wurtzite c-plane, a-plane, (11–22) semi-polar, and (001) cubic crystal orientations in self-consistent Schrödinger-Poisson and drift-diffusion models. We consider both structures strained to a GaN pn-junction and strain-reduced systems based on GaInN templates. In light of numerous experimental findings of the actual electric field strength, we find it necessary to reduce the piezoelectric coefficients over those commonly cited. A weaker variation with composition or wavelength is the consequence. For the non-polar and cubic systems, we find a 22% increase of the electron-hole overlap and an 18% increase for the c-plane strain-reduced system at an InN fraction of x = 0.30 when compared to standard c-plane structures. For the green and longer wavelength range, we find that strain-reduced and cubic GaN systems should hold particular promise for higher radiative efficiency.

By some accounts group-III nitride may be the widest disseminated man-made compound semiconductors. Yet, what is it that makes it so successful? Maybe the wurtzite structure which allows for piezoelectric polarization? We know about the Stokes shift it induces and its associated troubles. So we rush to reduce polarization in non-polar growth. But how about the cubic form of GaN. Shouldn't that be free of polarization? Would it be the better light emitter even? To find out we prepare GaN and GaInN/GaN heterostructures in cubic lattice form. By virtue of some patterning we achieve cubic growth on the more common form of Si, the (001) orientation, which further allows for conceptional integration with the semiconductor of industry choice. Group-III Structures and why their Structure MattersThe search for a wide bandgap semiconductor suitable for blue light emission has been a major motivation for the development of GaN and its related alloys with InN and AlN. Owing to a large bandgap of 3.42 eV it was kind of a conceptional stretch to consider it a semiconductor. Yet, with achievement of high crystalline GaN layers in heteroepitaxy on sapphire by help of low-temperature-deposited buffer layers, doping both, n-and p-type was enabled. 1 Then, alloying with even the slightest amounts of InN in GaInN layers, tremendous light emission efficiency was achieved leading to the rapid development of powerful blue LEDs which then could be used to pump suitable phosphor material to produce LEDs of white light perception. A theoretical description, let alone prediction of the electronic bandstructure of the group-III nitrides, however, proved a bit more challenging since the group-III nitride preferentially crystallize in the hexagonal wurtzite crystal structure, unlike all conventionally utilized semiconductors of the time being described in the cubic zincblende structure. A simple first approximation to describe a wurtzite lattice in the zincblende structure is imposing a superlattice onto zincblende along the (111) direction with a superlattice period of twice the layer spacing in that direction. This lifts the inversion degeneracy and allows for piezoelectric polarization. It also induces a zone folding leading to rather low lying secondary 10.1149/06607.0041ecst ©The Electrochemical Society ECS Transactions, 66 (7) 41-44 (2015) 41 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.117.10.200 Downloaded on 2015-07-18 to IP

Low-defect density non-polar a-plane Ga1-yInyN layers on r-plane sapphire substrates are reported by implementing self-assembling nanopatterning in metalorganic vapor phase epitaxy. Nanopillar capping and void formation in regrowth lead to a 90% defect reduction. An ex-situ Ni layer transforms into a nanoisland etch mask to pattern GaN templates. a-Plane GaN and Ga1-yInyN layers with an InN content in the range of y = 0.04–0.11 are then regrown. Both exhibit a low density of basal-plane stacking faults of (4.6 ± 1.3) × 104 cm−1 by transmission electron microscopy analysis. Growth parameters and the template pattern are discussed by help of an X-ray rocking curve analysis. We find pattern the fill factor and V/III ratio to dominate the defect reduction. Resulting layers should enable efficient long-wavelength light-emitting and solar cell devices.