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Wurtzite GaN epilayers bombarded at 300 K with 200 MeV 197 Au 16+ ions are studied by a combination of transmission electron microscopy (TEM) and Rutherford backscattering/channeling spectrometry (RBS/C). Results reveal the formation of near-continuous tracks propagating throughout the entire∼ 1.5-µ m-thick GaN film. These tracks,∼ 100Å in diameter, exhibit a large degree of structural disordering but do not appear to be amorphous. Throughout the bombarded epilayer, high-resolution TEM reveals planar defects which are parallel to the basal plane of the GaN film. The gross level of lattice disorder, as measured by RBS/C, gradually increases with increasing ion fluence up to∼ 10 13 cm-2. Based on these results, physical mechanisms of the formation of lattice disorder in GaN in such a high electronic stopping power regime are discussed. [ABSTRACT FROM AUTHOR]

This brief review focuses on defect and microstructural issues of importance for applications of ion irradiation of semiconductors. Ion irradiation of semiconductors can lead to a variety of disordering behaviour that depends not only on the semiconductor material but also on implantation parameters such as ion fluence, flux, energy and mass as well as the implantation temperature. In some cases, such as silicon implanted at or below room temperature, ion disorder leads readily to amorphization, whereas some other semiconductors, such as aluminium arsenide and gallium nitride, undergo very efficient dynamics annealing even at liquid nitrogen implantation temperatures and are difficult or even impossible to amorphize. In cases of efficient dynamic annealing a rich array, of defects can result during implantation. This presentation gives examples of the defect structures that can arise during implantation and subsequent annealing of semiconductors and illustrates how disorder can be exploited to advantage in both electronic and optoelectronic device applications. In particular, open volume defects such as voids and cavities can be generated in silicon and these can be used to selectively remove metal impurities. In compound semiconductors such as zinc oxide, ion irradiation can be used to introduce defects that raise the resistivity of the material by more than seven orders of magnitude. Finally, disorder can be used Io promote intermixing of the elemental constituents in adjacent multi-layer compound semiconductors and this process has been used to tune the wavelenglh of lasers. [ABSTRACT FROM AUTHOR]

The deformation behavior of rapidly grown tetragonal KD[sub 2x]H[sub 2(1-x)]PO[sub 4] (KDP and DKDP) single crystals, with a deuteration degree x of 0.0, 0.3, and 0.6, is studied by nanoindentation with a 1 μm radius spherical indenter. Within experimental error, the deformation behavior is found to be independent of the deuterium content and different for (001) and (100) surfaces. Multiple discontinuities (so-called “pop-in” events) in force-displacement curves are observed during indentation loading, but not during unloading. Slip is identified as the major mode of plastic deformation in DKDP, and pop-in events are attributed to the initiation of slip. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Depth profiles of [sup 1]H and [sup 2]D in rapidly grown KD[sub 2x]H[sub 2(1-x)]PO[sub 4] single crystals are studied by elastic recoil detection analysis. Results show that, under ambient conditions, deuteration in the first ∼500 nm from the sample surface significantly decreases within the first several days after D[sub 2]O surface polishing. This effect is attributed to deuterium–hydrogen exchange. The effective diffusion coefficient of this process is strongly dependent on both the degree of deuteration and the sample growth conditions. Physical mechanisms of D/H exchange are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Structural studies reveal that heavy ion bombardment of GaN causes amorphization and anomalous swelling of the implanted region as a result of the formation of a porous structure. Results strongly suggest that such a porous structure consists of N[sub 2] gas bubbles embedded into a highly N-deficient amorphous GaN matrix. The evolution of the porous structure in amorphous GaN appears to be a result of stoichiometric imbalance where N- and Ga-rich regions are produced by ion bombardment. Prior to amorphization, ion bombardment does not produce a porous structure due to very efficient dynamic annealing processes in the crystalline phase. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Wurtzite GaN films grown on sapphire substrates are studied by nanoindentation with a spherical indenter. No systematic dependence of the mechanical properties of GaN epilayers on the film thickness (at least for thicknesses from 1.8 to 4 μm) as well as on doping type is observed. Slip is identified as one of the physical mechanisms responsible for plastic deformation of GaN and may also contribute to the "pop-in" events observed during loading. No visible material cracking is found even after indentations at high loads (900 mN), but a pronounced elevation of the material surrounding the impression is observed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Wurtzite GaN films bombarded with heavy ions ([sup 197]Au[sup +]) show anomalous swelling of the implanted region with corresponding volume expansion up to ∼50%. Results show that this phenomenon is due to the formation of a porous layer of amorphous GaN. An important implication of this study for the fabrication of GaN-based devices is that amorphization of GaN should be avoided during ion implantation. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The damage buildup in wurtzite GaN films under light ([sup 12]C) and heavy ([sup 197]Au) ion bombardment at temperatures from -196 to 550 °C is studied by Rutherford backscattering/channeling spectrometry. A strong surface peak of lattice disorder in addition to the expected damage peak in the region of the maximum of nuclear energy loss has been observed for all implant conditions of this study. Capping of GaN with SiO[sub x] and Si[sub x]N[sub y] layers prior to implantation somewhat reduces but does not eliminate surface disordering. This suggests that nitrogen loss is not the main reason for the observed enhanced surface disorder, but, rather, the GaN surface acts as a strong sink for migrating point defects. However, pronounced loss of N during ion bombardment is observed for high dose implantation when the near-surface region is amorphized. Moreover, after amorphization, annealing at temperatures above about 400 °C leads to complete decomposition of the near-surface layer. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]