2, Université de Toulouse; LAPLACE; CNRS; INPT; UPS, Toulouse, , France
For diamond power electronic applications, such as transistors and diodes, substrate quality is a
key factor to obtain the best performances, influencing the properties of the epilayers. Moreover, understanding the properties of the substrate, especially doping level, is often necessary to design the devices accordingly.
In this work, Electron Beam Induced Current (EBIC) technique is used to visualize the lateral expansion of the depletion region of a Schottky contact (Ti/Pt/Au stack) deposited on a (100) HPHT high quality substrate provided by New Diamond Technology. A comparison with finite element simulation has been performed in order to quantify key parameters. This method, requiring a single lithography process, is demonstrated to be efficient to extract doping levels below 1016 cm-3, whereas SIMS measurements are only efficient for doping levels higher than this value. This method will be compared to previous measurements done by cathodoluminescence. The example presented in this work is a substrate having a p-type (Boron) doping level evaluated around 3.1015 cm-3 near the surface (up to a few micrometers away from the surface). Diffusion lengths of a few micrometers are extracted and compared with recent measurements done on boron doped epilayers . This method will also be applied to Nitrogen compensated substrates as a mean to test their electrical activity, prior to their use for devices.
 F. Omnes, et al., Diamond and Related Materials, vol. 20, no. 7, pp. 912–916, Jul. 2011.  H. Umezawa et al., Applied Physics Letters, vol. 110, no. 18, p. 182103, May 2017.