Near-field cathodoluminescence studies on n-doped gallium nitride films

Abstract

Articles you may be interested inNear-field cathodoluminescence ͑NFCL͒ has been used to characterize hydride vapor phase epitaxy grown n-GaN films. This technique can obtain high resolution luminescence images and perform local measurements of the diffusion length for minority carriers in different parts of the sample. NFCL contrast observed in round growth hillocks at the sample surface, with a diameter of less than 10 m, is compared with that observed by conventional cathodoluminescence in scanning electron microscope ͑CLSEM͒ techniques. In particular NFCL images reveal features not detected by CLSEM which is explained by the fact that under near field conditions the signal arises from a depth of only several tens of nanometers and is then directly related to the surface hillocks. Diffusion lengths of about 0.4 and 4 m have been found for the holes in different regions of the samples at room temperature. The order of magnitude of these minority carriers diffusion lengths is in good agreement with previous measurements performed at different GaN samples with other techniques. The NFCL contrast and the differences in the measured diffusion lengths are discussed and explained by variations in local trap concentrations.

GaN films deposited on glass substrate by middle-frequency magnetron sputtering

“…The surface of the GaN film prepared under the standard condition is composed of crystallites with various sizes. This surface structure is similar to nanocrystalline GaN film deposited on quartz by reactive radio frequency (RF) sputtering of GaAs target [1]. Fig.…”

“…Much attention has been paid to GaN recently for its application potential in electronic and optoelectronic devices, such as electron field emitter and light-emitting diodes in the blue, violet, and near-ultraviolet spectral ranges [1][2][3][4][5]. The conventional growth methods for GaN films are metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hydride vapor phase epitaxy (HVPE).…”

Preparation of GaN films on glass substrates by middle frequency magnetron sputtering

“…Considerable efforts have been devoted to GaN recently for its application potential in electronic and optoelectronic devices such as electron field emitter and light-emitting diodes (LED) in the blue, violet, and near-ultraviolet spectral ranges [1][2][3]. Traditional growth methods for GaN films such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and hydride vapor phase epitaxy (HVPE) are always at high temperatures ranging from 800 to 1000 1C.…”

Integrating electron and near-field optics: dual vision for the nanoworld

“…Nogales et al demonstrate the ability of near-field CL to image defects that are not seen in conventional CL [19], but also observed the challenge in interpreting topography effects superimposed on the near-field CL image because of the extremely high sensitivity of collection to the probe-specimen distance. Detailed quantitative image analysis that correlates topography changes to NSOM intensity changes, coupled to the transport imaging experiments that will be discussed in the next section, could be helpful in this regard for further isolating material luminescence variations.…”

“…Although diffusion lengths can in principle be estimated by scanning the electron beam with the collecting tip fixed at a point on the sample, as was discussed in [6] and [19], any variation in the generation location does change the nature of the experiment in a non-uniform material. The ability to scan the collecting tip enables the study of transport from a given point.…”