Photoluminescence from nanocrystallites embedded in hydrogenated amorphous silicon films prepared by plasma enhanced chemical vapor deposition

Abstract

We report in this letter the observation of visible photoluminescence (PL) at room temperature from nanocrystallites embedded in hydrogenated amorphous silicon films, which are prepared in a plasma enhanced chemical vapor deposition system by using strong hydrogen-diluted silane as the reactant gas source, without any post-processing. The PL is attributed to the radiative recombination process of carriers in the nanocrystallites, and the quantum size effect is responsible for the emission above the band gap of bulk crystal Si. The critical deposition parameters of this type of film are identified.

Silicon Porosification: State of the Art

“…As research have shown, deposited layers mainly represent nanocrystallites of silicon embedded in amorphous Si, SiO 2 or glass matrix. For example, Liu et al 361 have observed visible PL from nanocrystallites embedded in PECVD a-Si:H films. Usually the average size of such Si nanocrystallites was about 2 to 4 nm.…”

“…361 Si quantum structures can also be synthesized using a variety of techniques, which include rf cosputtering, 362,363 plasma decomposition of compounds, 364 highvacuum electron beam evaporation 365 and the most widely used Stranski-Krastanov mode of Molecular Beam Epitaxy (MBE). 366,367 We should note, however, that silicon, deposited or synthesized while using these methods, is not porous in the traditional sense, despite the presence of luminescence in the visible area of spectrum (see Figure 34).…”

Origin of photoluminescence in nanocrystalline Si:H films

“…However, similarly to PS [4,25], these films exhibit a PL improvement only after a post processing treatment, like oxidation and annealing in forming gas (H 2 -N 2 ). The deposition method of nanocrystalline silicon (nc-Si) films utilizing hydrogen diluted silane, commonly employed for the production of microcrystalline or polycrystallline silicon [26,27] has also been reported by Liu et al [28]. They reported the production of nc-Si grown at temperatures lower than 200 1C and exhibiting RT visible PL at 1.82 eV.…”

Nanocrystalline silicon prepared at high growth rate using helium dilution

“…Nano-Si films exhibit optical gap widening (Furukawa and Miyasato 1988;Das 2003), photoluminescence (Takagi et al 1990;Liu et al 1994;Mangolini et al 2005;Sankaran et al 2005), electroluminescence (Dehlinger et al 2000) and resonant tunneling (Fortunate et al 1989), as a consequence of three dimensionally confined quantum size effect. Photoluminescence quantum yield exceeding 60% has been reported by recent investigations (Jurbergs et al 2006).…”