Resistance formation mechanisms for contacts and to n-AlN and n-GaN with a high dislocation density

Sachenko, A. V.; Belyaev, A. E.; Boltovets, N. S.; Zhilyaev, Yu. V.; Kapitanchuk, L. M.; Klad'ko, V. P.; Konakova, R. V.; Kudryk, Ya. Ya.; Kuchuk, A. V.; Naumov, A. V., Panteleev V. V., Sheremet V. N.

We studied temperature dependences of the resistivity, <$E rho sub c (T)>, of Pd-Ti-Pd-Au ohmic contacts to wide-gap semiconductors n-GaN and n-AlN with a high dislocation density. Both <$E rho sub c (T)> curves have portions of exponential decrease, as well as those with very slight <$E rho sub c (T)> dependence at higher temperatures. Besides, the Au-Pd-Ti-Pd-n-GaN contacts have a portion of <$E rho sub c (T)> flattening out in the low-temperature region. This portion appears only after rapid thermal annealing (RTA). In principle, its appearance may be caused by preliminary heavy doping of the near-contact region with a shallow donor impurity as well as doping in the course of contact formation owing to RTA, if the contact-forming layer involves a material atoms of which serve as shallow donors in III - N compounds. The obtained <$E rho sub c (T)> dependences cannot be explained by the existing mechanisms of current transfer. We propose other mechanisms explaining the experimental <$E rho sub c (T)> curves for ohmic contacts to n-GaN and n-AlN.


	Наукова періодика України		Semiconductor physics, quantum electronics & optoelectronics