Structural Elements of Ultrashallow Thermal Donors Formed in Silicon Crystals

Abstract

It has been reported by one of the authors (A.H.) of the present study that ultrashallow thermal donors (USTDs) with a hydrogen-like electronic structure are formed in C- and N-doped O-rich Si crystals at approximately 450–600 °C. In this paper, it is reported that there are two types of USTDs: USTDs comprising C, H, and O [D(C,H,O)s] and USTDs comprising C, N, and O [D(C,N,O)s]. The thermal stability of these two types of donors was different; D(C,N,O)s were stable at 600 °C, while D(C,H,O)s were not stable at approximately 600 °C.

Ground-state splitting of ultrashallow thermal donors with negative central-cell corrections in silicon

“…2. 10,18,19) We observed new broad peaks, labeled A, B, and C in Fig. 1, as the temperature was increased to a higher range (20-50 K), despite the decreases in USTD and STD(H) intensities.…”

“…[6][7][8][9] In addition, a new type of shallow donor has been found in Si containing oxygen, nitrogen, and carbon. 10) Hydrogen is also an important element in Si-LSI circuits and solar cells, because various reactive gases including hydrogen are used in the thin-film growth process. Hydrogen is also important in the passivation and activation of impurities and defects.…”

“…17) We found ultrashallow thermal donors (USTDs) in carbonrich and hydrogen-doped Czochralski silicon (CZ Si) crystals. 10,18) USTDs are donors with a hydrogen-like electron structure but slightly different energy levels, some of which exhibit negative central-cell corrections. 10,18) To the best of our knowledge, these are the shallowest energy levels among the previously reported hydrogen-like donors in Si crystals.…”

“…10,18) USTDs are donors with a hydrogen-like electron structure but slightly different energy levels, some of which exhibit negative central-cell corrections. 10,18) To the best of our knowledge, these are the shallowest energy levels among the previously reported hydrogen-like donors in Si crystals. Note that USTDs are absent in carbon-lean and hydrogendoped CZ Si, as demonstrated in a previous report.…”

Mechanism of formation of ultrashallow thermal donors in carbon-doped oxygen-rich monocrystalline silicon preannealed to introduce hydrogen

“…Table I shows the peak positions observed in the Ref. 10, which correspond to USTDs-1 to -5 in Ref. 1, hydrogen-related thermal donors [STD(H)s]-2 and -3, and USTDs-1A and -2A.…”