We report the development of Al 0.7 Ga 0.3 N / AlN quantum wells with high internal quantum efficiency. All samples had identical well and barrier thickness but the III/V flux ratio was varied during growth by increasing the Ga flux. The luminescence spectra show single peaks which vary from 220 nm ͑III/ V ϳ 1͒ to 250 nm ͑III/ V ӷ 1͒ with internal quantum efficiency varying from 5% to 50%, respectively. To account for these results, a growth model was proposed in which at III/ V ϳ 1 the growth proceeds via vapor phase epitaxy, while at III/ V ӷ 1 the growth proceeds via liquid phase epitaxy.

We have developed a purely protein-based multilayered semiconducting 3D material using iron-storage protein ferritin. It is electronically homogeneous; capable of long range electron transport having a long exciton radius, and shows z-confinement.

A fiber-optic pump-probe setup is used to demonstrate all-optical switching based on intersubband cross-absorption modulation in GaN/AlN quantum-well waveguides, with record low values of the required control pulse energy. In particular, a signal modulation depth of 10 dB is obtained with control pulse energies as small as 38 pJ. Such low power requirements for this class of materials are mainly ascribed to an optimized design of the waveguide structure. At the same time, the intersubband absorption fully recovers from the control-pulse-induced saturation on a picosecond time scale, so that these nonlinear waveguide devices are suitable for all-optical switching at bit rates of several hundred Gb/s.

We propose that the growth of III‐Nitride semiconductors by plasma‐assisted MBE under Ga‐rich conditions takes place though the saturation of the liquid Ga covering the surface of the growing film with nitrogen, alloy constituents (aluminum and indium) and impurities. Thus, the proposed growth mode is a liquid phase epitaxy (LPE) rather than physical vapor phase epitaxy. While in traditional LPE growth the driving force is the gradient between the liquid and seed, in the proposed mode of MBE growth of nitrides the driving force is the concentration gradient due to the constant supply of active nitrogen, alloy components and impurities. The proposed LPE growth mechanism explains the relative temperature stability of GaN growth, the efficient doping with silicon and magnesium, and the selective desorption of oxygen and other impurities. Finally, the proposed LPE growth model can also account for the introduction of band structure potential fluctuations in AlGaN alloys, which improves their emission properties and leads to efficient deep UV‐LEDs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structures with incommensurate ordering along the [0001] direction are observed in wurtzite Al0.72Ga0.28N alloys grown by plasma-assisted molecular beam epitaxy on c-plane sapphire. Films grown in environments with group-III/N ratios greater than 1 exhibit ordered superlattice structures that are incommensurate with the wurtzite crystal lattice. In contrast, films grown under nitrogen-rich conditions exhibit ordered structures with a periodicity of four cation-N monolayers. The increasing complexity of the ordering with increasing Ga-rich growth environment suggests that the ordering is related to the presence of a Ga overlayer believed to exist on the surface of the growing film.