The amorphous silicon hydrogen alloys (ahyphen;Si:H) prepared by plasmahyphen;enhanced chemicalhyphen;vapor deposition are implanted with various impurities, i.e., phosphorus, silicon and boron, followed by 250thinsp;deg;C thermal annealing and hydrogen passivation. A critical phosphorus dosage of 5times;1015cmminus;2is found, beyond which the doping effect becomes evident and the electrical properities of the films are comparable to then+ahyphen;Si:H deposited by glowhyphen;discharge decomposition of SiH4and PH3. The silicon and boron implantation have less effect since the dosage is below 1015cmminus;2. It is found that the conductivity of the implanted sample after annealing is determined by three competing mechanisms, i.e., annihilation of the implanthyphen;induced defects, defect creation due to hydrogen evolution, and the impurity activation. From the IR spectra of the high dosage phosphorushyphen;implanted samples, a broad peak due to PHxradicals located from 2100 to 3500 cmminus;1is found. In addition, most of the voids are found to be filled by extra P ions during annealing, so very few hydrogen atoms can be driven into the film after hydrogen passivation. In photoluminescence spectra, the highhyphen;energy peak at 1.4 eV drops very quickly and the lowhyphen;energy shoulder at 1.25 eV becomes evident after implantation. It is found that Brodskyrsquo;s quantumhyphen;well model can be successfully applied to explain the observed results.
展开▼
