Optical Studies of Excess Carrier Recombination ina-Si: H: Evidence for Dispersive Diffusion

In-guide measurement of the infra red absorption variation induced in hydrogenated amorphous silicon by visible radiation

“…The 0.3 lm SiO 2 cladding layer was realized on the substrate by thermal oxidation, then the core on the top consisted of a 1.6 lm thick a-Si:H layer obtained by plasma enhanced chemical vapour deposition (PECVD). Because the presence of impurities can influence the deep traps density and the intensity of the PA phenomenon [5,8], differently doped a-Si:H cores have been deposited from silane (SiH 4 ) and diborane (B 2 H 6 ) gas mixture, at temperature and pressure of 170°C and 200 m Torr, respectively, with 3 h 15 min deposition time. Different gas phase doping ratios were used to deposit the cores of waveguides, as summarized in Table 1.…”

“…In a-Si:H, the NIR absorption involves dangling bonds states. These are deep levels in the gap and their occupation probability changes under pumping by photon with energy above the optical gap [4][5][6]. For this reason the NIR absorption of the illuminated material is higher than in the dark, then an all-optical amplitude modulation at fiber communication wavelengths can be easily obtained by illuminating the a-Si:H core of a waveguide by a suitable VIS pump source [7].…”

Study of in-gap defects in intrinsic and B-doped a-Si1−xCx:H by photo-induced optical absorption and photoluminescence

“…As the absorption in the IR region of the spectrum involves defect states in the band gap, it is assumed that the illumination with visible light changes the population of such states [7,8,10].…”

“…In particular, a micromodulator based on a-Si:H has been proposed, operating at the two communication wavelengths of 1300 and 1550 nm [4,5]. The device exploits the increase of the absorption in the IR region induced by the illumination with visible (VIS) radiation, a phenomenon commonly observed in amorphous semiconductors with tetrahedral coordination [6][7][8]. Therefore, the comprehension of the physical mechanisms underlying the phenomenon may be of great importance to optimize the performance of such micromodulator devices.…”

Origin of the non-exponential photocurrent decay in amorphous semiconductors

“…The T P method has provided useful information on carrier transport in localized tail states and carrier recombination (Schiff 1981, Pandya and Schiff 1983, Pfost, Vardeny and Tauc 1984, Zeldov and Weiser 1984.…”