Optical energy gaps are measured for high-quality Al 1−x In x N-on-GaN epilayers with a range of compositions around the lattice match point using photoluminescence and photoluminescence excitation spectroscopy. These data are combined with structural data to determine the compositional dependence of emission and absorption energies. The trend indicates a very large bowing parameter of Ϸ6 eV and differences with earlier reports are discussed. Very large Stokes' shifts of 0.4-0.8 eV are observed in the composition range 0.13Ͻ x Ͻ 0.24, increasing approximately linearly with InN fraction despite the change of sign of the piezoelectric field.

The authors have employed deep level transient spectroscopy to investigate the defects introduced in n-type Ge during 160keV indium (In) ion implantation. Our results show that In implantation introduces three prominent electron traps with energy levels at EC−0.09eV, EC−0.15eV, and EC−0.30eV, respectively. The authors have found that these defects are different from the point defects introduced by electron irradiation but that they do not involve In. Annealing at 600°C removed all the defects introduced during In implantation but results in a single prominent defect with a level at EC−0.35eV.

We have investigated structural and electrical properties of defects introduced during room temperature europium implantation into GaN. Two geometries, random and channeled implantation, were used. Rutherford backscattering and channeling analysis reveals that implantation induces a significantly lower concentration of defects, in the case of channeled implantation. These defects generate a perpendicular expansion of the GaN lattice in the implanted region, as evidenced by x-ray diffraction. From deep-level transient spectroscopy, beside intrinsic defects with energy levels below the conduction band, one additional electron trap, labeled Eu2, is observed at an energy (Ec−0.36eV). It is believed that this defect in n-GaN is europium related.

The lattice location of low-dose implanted Er in GaN, GaN:O, and GaN:C was investigated using the emission channeling technique. The conversion electrons emitted by the probe isotope 167m Er give direct evidence that the majority ͑Ϸ90%͒ of Er atoms are located on substitutional Ga sites for all samples. Annealing up to 900°C does not change these fractions, although it reduces the Er root-mean-square ͑rms͒ displacements. The only visible effect of oxygen or carbon doping is a small increase in the rms displacements with respect to the undoped sample.