Helium implanted gallium nitride evidence of gas-filled rod-shaped cavity formation along the c-axis

Abstract

The structural defects induced by He implantation in GaN epilayer at high fluence ͑1 ϫ 10 17 He/ cm 2 ͒ and elevated temperature ͑750°C͒ have been studied by conventional and high resolution transmission electron microscopy. In addition to the planar interstitial-type defects lying in the basal plane usually observed after high fluence implantation into GaN, a continuous layer of bubbles arranged in rows parallel to the implanted surface is observed in the region of maximum He concentration. This arrangement of bubbles is ascribed to interactions with dislocations. Beyond, one dimensional rod-shaped defects appear perpendicular to the implanted surface. Contrast analysis of high resolution images and atomistic simulations gives converging results in the determination of the nature and structure of these defects, i.e., gas-filled rod-shaped cavities in an overpressurized state.

Properties of helium bubbles in covalent systems at the nanoscale: A combined numerical and experimental study

“…As a result, the formation of gas-filled * julien.deres@univ-poitiers.fr extended defects such as platelets and bubbles is generally favored. This phenomenon is essentially independent of the host materials, since it has been reported in metals [6][7][8][9][10], covalent systems such as silicon [11][12][13][14][15][16][17][18][19][20], silicon carbide [21][22][23][24][25][26], gallium nitride [27], and disordered materials [28][29][30]. However, knowing why the bubbles form does not provide information about the formation mechanism itself, or about the properties of these bubbles.…”

Study of surface blistering in GaN by hydrogen implantation at elevated temperatures

“…Therefore, no platelets formed in the as-implanted sample can explain why the threshold dose for splitting in H-implanted GaN is almost one order of magnitude larger than that of H-implanted Si or SiC. Barbot et al [24] reported the formation of gas-filled platelets along the caxis in the GaN crystalline implanted with He ions at 750°C to a fluence of 1 × 10 17 cm − 2 . The platelets are only observed in the end of the projected range where the vacancy concentration is rather low as compared to the He concentration.…”

Synthesis of mesoporous amorphous silica by Kr and Xe ion implantation: Transmission electron microscopy study of induced nanostructures

“…Nevertheless, when the fluence increases, a small shift of the bubble distribution occurs towards the implantation damage profile, indicating that damage concentration is getting closer to the threshold. Implanting to a higher dose (>5 Â 10 16 Kr/cm 2 ) should lead to the formation of a bubble band centred on the simulated damage peak. The formation of bubbles all along the Kr profile and even beyond, where very small amounts of Kr and damage are expected, is proof that the complexes Kr-vacancy-type defect are mobile and are able to spread resulting in the observed plateau distribution.…”

“…The formation of bubbles in amorphous material seems to be quite different than in crystalline materials. It is well known that noble gas implantation into crystalline materials such as Si [14], SiC [15], GaN [16] leads to the formation of tiny bubbles of 1-3 nm in size. Recently it was shown that He implantation in amorphous silicon leads to the formation of significantly larger bubbles compared to those observed in crystalline Si under identical implantation conditions [17].…”