Hyperfine Structure of the Electron Spin Resonance of Phosphorus-Doped Si Nanocrystals

Abstract

Electronic states of P donors in Si nanocrystals (nc-Si) embedded in insulating glass matrices have been studied by electron spin resonance. Doping of P donors into nc-Si was demonstrated by the observation of optical absorption in the infrared region due to intraconduction band transitions. P hyperfine structure (hfs) was successfully observed at low temperatures. The observed splitting of the hfs was found to be much larger than that of the bulk Si:P and depended strongly on the size of nc-Si. The observed strong size dependence indicates that the enhancement of the hyperfine splitting is caused by the quantum confinement of P donors in nc-Si.

Energetics and carrier transport in doped Si/SiO2quantum dots

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] In particular, it has been shown that electrically-activated impurity atoms located in substitutional sites tend to enhance the conductivity. [6][7][8][9][10] Theoretically, several works have studied the formation and ionization energies, and the opto-electronic properties of freestanding doped SiQDs.…”

Phosphorus ion implantation in silicon nanocrystals embedded in SiO2

“…The donor level in SiNCs has been known to be a little bit deeper ͑ϳ60 meV͒ than that ͑ϳ40 meV͒ of bulk crystal Si from larger ESR splitting of the hyperfine structure of P donors in SiNCs. 3,4 Since the numbers of Si atoms contained in each SiNC with diameters of 3 and 5 nm are estimated to be approximately 680 and 3100, the number of allowed levels near the bottom of the discrete conduction band of each SiNC is much smaller compared to the states near the bottom of the continuum conduction band of bulk Si. Consequently a fraction of donor electrons is still bound by donor levels in SiNCs even at RT, which is entirely different from donors in bulk Si.…”

“…Fujii and co-workers 3,7 reported P doping effects for PL intensity that light doping produces enhancement of PL for SiNCs with relatively small sizes, but not for those for larger SiNCs, and heavy P doping leads to decrease in PL intensity. The latter is due to Auger nonradiative recombination.…”

“…It has been already understood that quantum confinement is an origin for the blue shift photoemission from Si nanostructures, and that shallow level impurities such as phosphorus ͑P͒ donor and boron ͑B͒ acceptor in bulk crystal Si have slightly deeper, but still shallow levels even in SiNCs less than approximately 10 nm. 3,4 For nanoelectronics using semiconductors, impurity doping will continue to be very important for control of carrier concentration leading to control of the electrical conductivity and for control of the efficiency of light emission such as photoluminescence ͑PL͒ and electroluminescence. 1,2,5 While as an impurity doping technique, only ion implantation has been developed especially for Si-LSI processes since 1970s, it has been used also in formation of SiNCs in SiO 2 , 1-3 defect production, 6 and impurity doping 1 in SiNCs.…”

“…3,7 For investigation of ion implantation effects in silicon ͑Si͒ nanostructures, we have measured PL and electron spin resonance ͑ESR͒ of un-doped SiNCs and P doped SiNCs embedded in SiO 2 before and after hydrogen passivation. We call hereafter these systems SiNCs/ SiO 2 , for simplicity.…”