Effect of Hydrogen Dilution on Structure and Electronic Properties of Ge:H and Ge_YSi_1-Y Films Deposited by Low Frequency Plasma

Abstract

We report on a systematic study of growth rate, surface morphology, hydrogen and oxygen incorporation, optical and electrical properties in Ge:H and Ge Y Si 1-Y :H, Y> 0.85 films, deposited in a capacitive reactor by low frequency PE CVD. Silane and germane were used as feed gases diluted by hydrogen. Hydrogen dilution is characterized by R= Q H2 /[Q SiH4 +Q GeH4 ], where Q H2 , Q SiH4 , and Q GeH4 are gas flows of hydrogen, silane and germane, respectively. The flow was varied in the range of R=20 to 80. Composition of the films was characterized by SIMS profiling. We did not observed a significant change of the deposition rate V d in Ge Y Si 1-Y :H films over the range of R, while for Ge:H films V d was significantly reduced for R>50. AFM characterization of the surface morphology demonstrated that at R=50 average height <H>(R) reached a maximum in both Ge:H and Ge Y Si 1-Y :H films, while average diameter <D>(R) had a minimum in Ge Y Si 1-Y :H films and maximum in Ge:H films. Both Ge:H and Ge Y Si 1-Y :H films demonstrated a change of E 04 in the studied range of R, and a minimum clearly appeared in ∆E at R=50-60 suggesting significant reduction in weak bonds of these films. The activation energy of conductivity E a slightly increases with R in Ge:H films and shows no definitive trend in Ge Y Si 1-Y :H: films. Both FTIR and SIMS data show a general trend of decreasing hydrogen and oxygen content with R. These two types of films showed different behavior and correlations between surface morphology and optical and electrical properties.

Nano-structured GeySi1-y:H Films Deposited by Low Frequency Plasma for Photovoltaic Application

“…Conductivity of the films correlated clearly with structure as illustrated by Table 1 for several samples, more detailed information could be found in [11]. Changing germanium content resulted in change activation energy E a mainly due to reducing optical gap E g .…”

“…Our previous study [10][11][12] has revealed a significant effect of hydrogen dilution R H on microstructures, hydrogen incorporation and electronic properties. It was observed that optimization of deposition conditions and especially of R H could result in rather well organized microstructure with narrow distribution function of nano-grains over heights and diameters (i.e.…”

Noise in Different Micro-bolometer Configurations with Silicon-Germanium Thermo-sensing Layer

“…The fabrication process flow has been previously described in ref. [10]). The IR absorber, support and protective layers (SiN x ), and the thermosensing layer (a-Si x Ge y B z :H) were deposited by low frequency plasma (LF PECVD).…”