The doped microcrystalline silicon films have been deposited by the radio frequency(13.56MHz) glow discharge decomposition of $SiH_2F_2 + B_2H_6 + H_2$ and $PH_3 + SiH_2F_2$ mixing gases with varying substrate temperature (100℃ ~ 310℃) and rf power density (160mW/㎠~ 530mW/㎠). With increasing substrate temperature, growth rate decreases up to 200℃ and then increases slowly at low rf power level. The growth rate not changes with substrate temperature at high rf power level. It was found that the chemical equilibrium between the deposition and etching of Si on the growing surface formed microcrystalline Si. The microcrystalline Si was confirmed from X-ray diffraction and Raman scattering.
A new method of the fabrication, layer by layer deposition technique, with hydrogen radical annealing in between have been studied to accomplish the high stability in a-Si:H films with preparation parameters of substrate temperature and hydrogen plasma exposure (HPE) time. With the increase of HPE time, the dark conductivity decrease up to 15 sec and then increases rapidly, resulting in that maximum photosensitivity 3×$10^6$ can be reached by about 15 sec of HPE time. Above 50 sec of HPE time the microcrystalline Si is formed, confirmed from the dark conductivity.
It was found from the experiments that the deposition rate per cycle of the film decreased monotonously in proportion to the hydrogen plasma exposure time, indicating that the deposited film is etched slightly during the hydrogen plasma exposure. As results, a-Si:H films produced by layer by layer deposition technique having photosensitivity of >$10^6$, conductivity activation energy of 0.9 eV, and hydrogen content of <10 at.% were obtained. The Staebler-Wronski effect of this films is greatly reduced compared with single-layered a-Si:H film deposited at the same temperature.
주기적인 증착방법(layer by layer deposition technique)을 이용하여 PECVD장치에서 기판의 온도를 270℃와 310℃로 고정하고 각각의 온도에서 수소 플라즈마 노출 시간을 0초 ~50초까지 변화 시키면서 수소화된 비정질 규소를 제작하였다.
암전기 전도도의 활성화에너지가 0.9 eV이상으로 중간갭 까지 Fermi level이 깊이 내려감을 알았고 광감옹도도 약 $3.5 \times 10^6$ 정도로 개선이 되었으며 같은 온도에서 conventional하게 제작한 시료보다 SWE가 적게 일어남을 알았다.
또한 CPM결과 Urbach tail이 매우 작은 값을 가지는데 이는 각 주기마다 수소원자가 노출되어 시료에 어떤 미시적인 구조 변화를 준 결과라고 생각된다. 즉 수소가 약한 Si 결합을 etching 하고 dangling bond를 포화 시켜 준 결과이다.