Effects of Implantation Temperature on Sheet and Contact Resistance of Heavily Al Implanted 4H-SiC

Abstract:

Effects of implantation temperature on electrical properties of heavily-Al-doped 4H-SiC layer formed with Al implantation have been investigated. To form the p++ 4H-SiC with the original 4H-stacking structure, the implantation temperature above 175 °C is needed. A decrease in the implantation temperature below 250 °C leads to an increase in the NA-ND. It is suggested that an increase in the density of vacancies with a decrease in the implantation temperature promotes the Al substitution to lattice sites during activation annealing. The lower-temperature implantation also causes a decrease in activation energy for the p-type electrical conduction and a decrease in p-type ohmic contact resistivity. We presume that the increase in the Al acceptors at low-implantation temperatures gives expansion of the impurity bands and formation of valence band tail-states, causing the decrease in the impurity binding energy. The properties obtained with the lower-temperature implantation are desirable for practical applications especially at low temperatures.

• Periodical: Materials Science Forum (Volumes 645-648)
• Pages: 705-708
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.645-648.705
• Online since: April 2010
• Authors: Tomokatsu Watanabe, Sunao Aya, Ryo Hattori, Masayuki Imaizumi, Tatsuo Oomori
• Keywords: Aluminum Ion Implantation, Contact Resistance, Sheet Resistance

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[60] [80] 100 120 1401 2 3 4 5 6 Activation energy (meV) NA-ND (cm-3) [x1019] ○ 1500℃ △ 1700℃.

[2] [4] [6] [8] [10] [12] [14] 200 300 400 500 600 Rcontact (m Ω cm2) T (K).

[2] [4] [6] [8] [10] [12] [14] 200 300 400 500 600 T (K) (b) (a) ○ 175 ˚C △ 200 ˚C □ 250 ˚C ● 300 ˚C ▲ 500 ˚C ○ 175 ˚C △ 200 ˚C □ 250 ˚C ● 300 ˚C ▲ 500 ˚C.