As the size of semiconductor devices continues to shrink, the normally random distribution of the individual dopant atoms within the semiconductor becomes a critical factor in determining device performance—homogeneity can no longer be assumed1,2,3,4,5. Here we report the fabrication of semiconductor devices in which both the number and position of the dopant atoms are precisely controlled. To achieve this, we make use of a recently developed single-ion implantation technique6,7,8,9, which enables us to implant dopant ions one-by-one into a fine semiconductor region until the desired number is reached. Electrical measurements of the resulting transistors reveal that device-to-device fluctuations in the threshold voltage (Vth; the turn-on voltage of the device) are less for those structures with ordered dopant arrays than for those with conventional random doping. We also find that the devices with ordered dopant arrays exhibit a shift in Vth, relative to the undoped semiconductor, that is twice that for a random dopant distribution (- 0.4 V versus -0.2 V); we attribute this to the uniformity of electrostatic potential in the conducting channel region due to the ordered distribution of dopant atoms. Our results therefore serve to highlight the improvements in device performance that can be achieved through atomic-scale control of the doping process. Furthermore, ordered dopant arrays of this type may enhance the prospects for realizing silicon-based solid-state quantum computers10.
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This work was partly supported by the Special Coordination Funds for Promoting Science and Technology, Center of Excellence (COE) research programme and the 21st-century Center of Excellence (21COE) programme from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank Y. Shinoda for his critical reading of the manuscript. Author Contributions The experiment was planned by T.S. Samples were prepared, and their electrical properties measured, by T.S., S.O. and T.K. SII was invented by I.O.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
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