(Invited) Effect of Individual Dopants in Nano-SOI-MOSFETs and Nano-pn-Diodes

Tuesday, October 13, 2015: 16:00
103-B (Phoenix Convention Center)
M. Tabe (Research Institute of Electronics, Shizuoka University), D. Moraru (Shizuoka University), A. Samanta, K. Tyszka (Shizuoka University, Warsaw University of Technology), H. N. Tan (Shizuoka University), Y. Takasu (Shizuoka University), R. Jablonski (Warsaw University of Technology), L. T. Anh (Japan Advanced Institute of Science and Technology), H. Mizuta (Japan Advanced Institute of Science and Technology, University of Southampton), and T. Mizuno (Shizuoka University)

In recent years, novel MOSFET characteristics dominated by a single dopant-atom were reported by several groups [1-4], where carrier transport mechanism is tunneling through individual dopant atoms. In this background, we have proposed and demonstrated a variety of dopant-atom devices, i.e., dopant-atom (DA) transistors [4], DA memories [5], DA turnstiles [6-8] and DA photonic devices [9-11]. In those devices, only one or a few dopants are intentionally used and one dopant works as a quantum well for electron (or hole) tunneling transport. Here, we present a brief overview of such devices from experimental and theoretical point of view.

P-donor in nano-Si

When we focus on a phosphorous (P) donor atom, it is known that the ionization energy, or the binding energy, with respect to the Si conduction band minimum, is ~45 meV. Therefore, single-electron tunneling P-atom devices can operate only at low temperatures, below ~20 K, since at high temperatures electrons are thermally excited and tunneling transport mechanism does not work. However, when a dopant is embedded in sufficiently small Si structures, its ionization energy is enhanced due to dielectric and quantum size confinement effects [12], leading to high-temperature operation.

Recently, we have demonstrated operation of donor-atom SOI-MOSFETs at around 100 K in specifically-designed nano-stub-channels [13]. A good correlation is found between the operation temperature and binding energy (Ea), with the highest SET-operation temperature being achieved for a P donor with Ea≅ 100 meV [13].

A few coupling donors

So far, in most investigated dopant-atom devices, the dopants were introduced in random positions. Only a few works addressed directly the control of dopants, either in number, using single ion implantation [14], or in position, with atomic manipulation using scanning tunnelling microscope tips [15]. Most recently, we have challenged a more practical and simpler doping technique using nanoscale doping masks [16]. The channel of SOI-MOSFET was selectively doped within an area of ~30 nm in width by the conventional diffusion process. Even in such a classical doping process, the number of dopants in the doped area may be controlled to around 5. I-V characteristics measured for these selectively-doped FETs are consistent with the model [16].

Nano-pn junctions

Individuality of dopants appears not only in nano-FETs, but also in nano-pn diodes. In fact, we have reported dopant-induced random telegraph signals (RTS) in nanoscale pn diodes [17], and attributed the RTS to charging and discharging of a single dopant near the pn junction.

Observation of dopant potential

In research of dopant-atom devices, it is extremely important to establish an observation tool to monitor dopants’ positions and their individual potentials. For this purpose, we have developed low-temperature Kelvin probe force microscopy (LT-KFM) which allows measurements of devices under regular operation. Using this technique, we succeeded in detection of potential profiles due to individual dopants and potential changes due to single-electron injection effects [18-21].


[1] H. Sellier et al: Phys. Rev. Lett. Vol. 97 (2006), p. 206805.

[2] G.P. Lansbergen et al: Nature Phys. Vol. 4 (2008), p. 656.

[3] Y. Ono, et al: Appl. Phys. Lett. Vol. 90 (2007), p. 102106.

[4] M. Tabe et al: Phys. Rev. Lett. Vol. 105 (2010), p. 016803.

[5] E. Hamid et al: Appl. Phys. Lett. Vol. 97 (2010), p. 262101.

[6] D. Moraru et al: Phys. Rev. B Vol. 76 (2007), p. 075332.

[7] D. Moraru et al: Appl. Phys. Express Vol. 2 (2009), p. 071201.

[8] K. Yokoi et al: J. Appl. Phys. Vol. 108 (2010), p. 053710.

[9] M. Tabe et al: Phys. Stat. Sol. A Vol. 208 (2011), p. 646.

[10] A. Udhiarto et al: Appl. Phys. Lett. Vol. 99 (2011), p. 113108.

[11] A. Udhiarto et al: Appl. Phys. Express Vol. 5 (2012), p. 112201.

[12] M. Diarra et al: Phys. Rev. B Vol. 75 (2007), p. 045301.

[13] E. Hamid et al: Phys. Rev. B Vol. 87 (2013), p. 085420.

[14] E. Prati et al: Nature Nanotechnol. Vol. 7 (2012), p. 443.

[15] M. Fuechsle et al: Nature Nanotechnol. Vol. 7 (2012), p. 242.

[16] D. Moraru et al: Sci. Rep. Vol. 4 (2014), p. 6219.

[17] S. Purwiyanti et al:  Appl. Phys. Lett. Vol. 103 (2013), p. 243102.

[18] M. Ligowski et al: Appl. Phys. Lett. Vol. 93 (2008), p. 142101.

[19] M. Anwar et al: Appl. Phys. Lett. Vol. 99 (2011), p. 213101.

[20] M. Anwar et al: Jpn. J. Appl. Phys.  Vol. 50 (2011), p.  08LB10.

[21] R. Nowak et al: Appl. Phys. Lett. Vol. 102 (2013), p. 083109.