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Control of vacancy-type defects in Mg implanted GaN studied by positron annihilation spectroscopy

Material and application

Gallium Nitride (GaN) is used as a wide band gap semiconductor (Egap = 3.4 eV) for applications in next generation high power electronics. For device structure fabrication the controlled doping within selective areas is essential. The most common technique to control carrier concentrations is ion implantation (e.g. with Mg+) . A drawback of this technique is the creation of defects in the lattice, which leads to unwanted changes in the electronic properties. However, these defects can be reduced by high temperature annealing.

What was the research question to be solved

Which kind of defects are generated by Mg+ ion implantation with energies between 20 – 430 keV? How does subsequent temperatures treatment influence these defects? Is the annealing process influenced by Hydrogen impurities?

What results did the PALS method provide

Different defect types and their relative occurrence after Mg+ and/or H+ could be observed. The major defect species was determined to be VGa related defects such as VGaVN and/or their complexes with impurities. Samples without H+ implantation started to form defect clusters at annealing temperatures between 800 – 1000°C. This process was suppressed for samples with H. The basic mechanism behind this result is assumed to be the formation of complexes between Mg atoms located at Ge sites and H atoms.

What was the impact of the achieved result for the user

The results show that Mg+ ion implantation creates different kinds of defects inside the GaN lattice. The crystal can be annealed with temperatures between 800 – 1000°C, when the defects start to migrate and form larger vacancy clusters. However, the occurrence of H impurities prevent the annealing process.

Reference, scientific publication

Control of vacancy-type defects in Mg implanted GaN studied by positron annihilation spectroscopy
A. Uedono, M. Dickmann, W. Egger, C. Hugenschmidt, S. Ishibashi, S. F. Chichibu Gallium Nitride Materials and Devices XV Proceedings Volume 11280 (2020)

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