Dependences of the diffusion coefficient and the lifetime of photoexcited carriers in undoped microcrystalline silicon ( μc-Si) on the volume fraction and the grain size were observed by a transient grating method and the dynamics of photexcited carriers is discussed. Under the condition of a constant grain size, the lifetime decreases with the increase of the volume fraction but the diffusion coefficient increases with the increase of the volume fraction for any fraction larger than 0.2. The dependence of the lifetime was explained well by a carrier recombination at grain boundary regions. The dependences of the diffusion coefficient and the dark conductivity were interpreted by a percolation process.

Semi-insulating Cr-doped single-crystal GaAs samples were implanted at room temperature with 300-keV Si ions in the dose range of (0.17–2.0)×1015 cm−2 and were subsequently steady-state annealed at 900 and 950 °C for 30 min in a H2 ambient with a Si3N4 coating. Differential Hall measurements showed that an upper threshold of about 2×1018/cm3 exists for the free-electron concentration. The as-implanted atomic-Si profile measured by SIMS follows the theoretical prediction, but is altered during annealing. The Cr distribution also changes, and a band of dislocation loops ∼2–3 kÅ wide is revealed by cross-sectional TEM at a mean depth of Rp∼3 kÅ. Incomplete electrical activation of the Si is shown to be the primary cause for the effect.

Carrier dynamics at a free surface and an interface in a glow discharge hydrogenated amorphous silicon (a:Si:H) film were observed by a transient grating method. The diffusion coefficients and lifetimes at the surface and in the bulk were determined separately by exciting carriers by selecting the wavelength of the excitation light. The diffusion coefficients and lifetimes in the bulk, at the surface and interfaces decreased in the following order: bulk, a:Si:H free surface, a-Si:H/substrate interface, a-Si C:H/a-Si:H interface.

A systematic investigation has been made on steady-state and time-resolved photoluminescence (PL) in microcrystalline silicon (μc-Si) at liquid-helium temperature. The steady-state PL spectra on various grain sizes and volume fractions are examined. It is found that the low-energy emission (∼0.76 eV) arises only from the amorphous phase and not from the crystalline phase and the grain boundary regions. The results indicate that the origin of the luminescence is considered to be due to defects created in the amorphous phase resulting from the microcrystallinity which increase with the grain size and/or the volume fraction. It has been shown from the analysis of the time-resolved PL measurement that the recombination transition of carriers of the low- and the high- (∼1.24 eV) energy emissions can be interpreted by a new model.

Articles you may be interested inRefractive index control of silicon nitride films prepared by radio-frequency reactive sputtering Magnetic and structural properties of iron nitride thin films obtained by argonnitrogen reactive radiofrequency sputtering J. Appl. Phys. 77, 5309 (1995); 10.1063/1.359286Indium nitride thin films prepared by radiofrequency reactive sputtering Cr-N films were synthesized successfully on the stainless steel and the high-speed steel plates by rf reactive ion plating. Cr was evaporated from an electron beam evaporator into the N2 or NH3 gas plasma at the pressure of the order of 10-2 Pa. The optimum net rfpower to synthesize was about 200 W. The amount of Cr and N atoms contained in the synthesized layer were measured by Auger electron spectroscopy. The crystal structure of the layer was analyzed by x-ray diffraction and reflection high energy electron diffraction. The resulting Cr-N films formed by rfreactive ion plating had two types of crystal structures composed of fJ-Cr2N and CrN, and the type of structure was able to be controlled easily by the ion plating conditions. The structure of the hardest film was found to be fJ-Cr2N (hexagonal structure) by micro-Vickers method. All the films synethsized under the various conditions by the method were observed to be composed of small size grains with microcracks.