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- Title
Observation of the potential distribution in GaN-based devices by a scanning electron microscope.
- Authors
Karumi, Takahiro; Tanaka, Shigeyasu; Tanji, Takayoshi
- Abstract
Mapping of the potential distribution using a scanning electron microscope (SEM) has been reported in recent years [1,2] for semiconductors such as Si, GaAs and InP. But, there are no such studies on GaN-based devices, to our knowledge. In this study, we observed two types of GaN-based devices by SEM to see if there is a condition that the contrast matches the potential distribution of the devices. The first device we studied was GaN p-n junction (p, n ∼5 × 1017 cm−3). The device was cut, and polished from the cross-section to a flat surface. The cross-section was observed by SEM. Fig. 1(a) shows an SEM image taken at 3 kV. The p-region appears bright and the n-region appears dark. The image intensity changes at the position of p-n junction, for which we used electron beam induced current (EBIC) technique to determine the p-n junction position. Fig. 1(b) is a line profile across the p-n junction (broken line) of the SEM image together with a calculated potential distribution (solid line) using p and n concentrations. It can be seen that the contrast profile matches the potential distribution very well. The SEM observations were carried out for several accelerating voltages. But, best result was obtained at 3 kV. For lower accelerating voltages, the image seemed to reflect the surface potential. On the other hand, higher accelerating voltages resulted in blurred images. The second sample was a light emitting diode structure based on AlN where a multiple quantum well (MQW) structure was sandwiched by p- and n-AlGaN materials. In this case, the sample was obliquely polished from the surface (∼10°) to improve the lateral resolution. The SEM image could reveal the structure of MQW.Fig. 1.(a) SEM image of p-n GaN. (b) Comparison of line profile across the p-n junction (broken line) and a calculated potential distribution (solid line).AcknowledgementWe thank professor H. Amano (Nagoya University) for providing the samples.
- Subjects
GALLIUM nitride; SCANNING electron microscopes; SEMICONDUCTORS; ELECTRON beam induced current; QUANTUM wells
- Publication
Microscopy, 2014, Vol 63, Issue suppl_1, pi22
- ISSN
2050-5698
- Publication type
Article
- DOI
10.1093/jmicro/dfu051