Recently, owing to their wide direct band gap, GaN materials have used increasingly in the field of commercial industries, such as back lighting of liquid crystal display device, white light, traffic light and car lighting. To improve the efficiency of GaN devices, it is necessary to achieve high P-type doping levels of 10¹⁹~10²⁰ cm^-3. However, in Mg doped p-type GaN, native defects, residual impurity and complexes passivate or compensate Mg acceptors during growth [1-5]. The ability to control the Mg concentration and the other impurities during the p-GaN growth will lead to improved GaN device quality and functionality [5]. Therefore, it is important to know Mg doping distributions and concentrations in p-GaN.

In this study, electron holography, scanning capacitance microscopy (SCM), and cathodoluminescence (CL) were used to obtain two-dimensional doping profile of Mg doped p-type GaN. The samples were grown by Metal Organic Chemical Vapour Deposition (MOCVD) and consist of alternating 250nm layers of un-doped GaN and Mg doped GaN. We were prepared for electron holography measurement using FIB (focused ion milling) with low kV milling for which samples was removed ion damage layers. Successfully, we obtained quantitative doping profile with Mg doped p-type GaN. We compared the doing profiles of electron holography, SCM, and CL to secondary-ion mass spectrometry (SIMS) data and discussed their results.

Reference

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[2] U. Kaufmann, M. Kunzer, M. Maier, H. Obloh, A. Ramarkishnan, b. Santic, and P. Schlotter, Appl. Phys. Lett. 76, 1326 (1998).

[3] F. Shahedipour, and B. W. Wssels, Appl. Phys. Lett. 76, 3011 (2000).

[4] O. Gelhausen, H. N. Klein, M. R. Phillips, and E. M. Goldys, Appl. Phys. Lett. 81, 3747 (2002).

[5] O. Gelhausen, M. R. Phillips, and E. M. Goldys, J. Phys. D: Appl. Phys. 36, 2976 (2003).

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1. Investigations of GaN-Based Heterostructures with Scanning Capacitane Microscopy