[en] Experimental evidence is presented that both the initial and light-induced deep defects in high-quality undoped a-Si:H are generated by the same mechanism. A material in which it is easier to generate defects will therefore exhibit both more initial defects and a higher susceptibility to light-induced degradation. These effects tend to balance each other in such a way as to make the absolute increase in the number of states added by a given light-soak be about the same over a wide range of film quality. Thus the relative change in the number of states is greater for higher-quality (lower initial defect-density) material. Evidence is presented that the defect-generating mechanism is related to strained bonds. Thus microstructural profiles with associated strain profiles can lead to profiles in both initial defect density and light-induced susceptibility

[en] Hydrogenated amorphous silicon-selenium alloy thin films were grown by capacity coupled radio frequency glow discharge decomposition of (SiH/sub 4/ + He) and (H/sub 2/S + He) gas mixtures. In this work we report on a study to correlate the deposition parameters of a-Si, Se:H thin films with its optical, electronic and spectroscopic properties. The alloy composition was varied by changing the gas volume ratio R/sub v/ = [H/sub 2/Se]/[SiH/sub 4/]. The films are characterized via infrared spectroscopy, photoconductivity, photoluminescence, constant current method and conductivity measurements. (author)

[en] The vibrational and electronic properties of novel non stoichiometric a-St:H with the chalcogen atoms was found to produce a greater degree of disorder and an increase that S and Se atoms are primarily bonded to Si within the solid matrix. The optical energy gap was found to increase in proportion to the amount and binding energy of incorporated chalcogen atoms. (author)

[en] Changes in the minority carrier diffusion length, in reverse-bias photocurrent and dark current of thin films of amorphous silicon germanium alloys (a-SiGe:H,F) caused by prolonged illumination with AM1 light were compared with changes caused by irradiation with 12 MeV protons. Both light soaking and proton irradiation degrade the μ tau products of electrons and holes while introducing metastable defects. The time needed to reduce the photocurrent by one order of magnitude in Schottky barrier structures containing a 2 μm thick film of a-Si:H and a-SiGe:H was 8 min and 15 min, respectively. Comparable degradation in a-Si:H and a-SiGe:H,F samples due to illumination with AM1 light is reached after several hundred hours. In a-Si:H the diffusion length decreased from 0.2 μm to near the measurement limit of 0.03 μm. While having similar effects, proton irradiation can be performed on a much shorter time scale than light soaking

[en] Photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM) are used to monitor the changes in density of deep defects associated with the Staebler-Wronski effect. These values are correlated with the electron spin resonance (ESR) signal, dc photoconductivity, and minority-carrier μ tau values determined from bias-dependent carrier collection efficiency studies. The density of deep defects determined by subgap absorption grows with light-soaking time t following the same function form (t/sup 1/3/) as the ESR signal. The initial and light-induced defects have similar carrier recombination cross-sections

[en] Hydrogenated amorphous silicon sulphur thin films were grown by capacitively coupled radio frequency glow discharge decomposition of SiH/sub 4/ + He) and H/sub 2/S + He) gas mixtures. In this work we report on a study undertaken to instigative the effect of deposition conditions on the optoelectronic properties of a-Si,S:H films. Three series of deposition conditions on the optoelectronic properties of a-Si,S:H films. Three series of films were prepared using a constant flow rate of the gaseous mixture while varying one of the other deposition parameters: substrate temperature, RF powder and process pressure. The films are characterized via IR measurements, optical transmission, photothermal deflection spectroscopy, photoluminescence, the constant photocurrent methods and conductivity measurements. Results indicate that a relatively high power level and a high substrate temperature are necessary to obtain the best films. (author) 8 figs

[en] The electronic and optical properties of a-Si,Ge:H,F alloys are investigated for the initial (as-grown) state as well as after annealing, light soaking, and subsequent annealing. The optical absorption spectra were determined from optical transmission, the constant photocurrent technique and photothermal deflection spectroscopy. The photoconductivity and the temperature dependence of the dark conductivity were measured. A post-deposition anneal was found to improve the measured properties for some of the alloys. The properties of the high gap, E/sub opt/ > 1.4 eV, and the low gap, E/sub opt/ < 1.4 eV, alloys change differently with light soaking. For the high gap alloys, there is an increase in the subgap absorption, a decrease in the photoconductivity and the dark conductivity and an increase in the activation energy with light exposure. The gap alloys show increasing subgap absorption with light soaking, however, the photoconductivity remains constant and the dark conductivity increases and its activation energy decreases

[en] The authors report a new technique for measuring the density distribution of the D⁰-/ state in a-Si:H before and after light soaking and in a-Si,Ge:H,F alloys. Electron time-of-flight (TOF) measurements as a function of temperature from the basis of their new technique. The deep trapping of electrons controls the mobility-lifetime product (μtau)_n, which is evaluated from the integrated TOF current. The dominant deep trap is the D⁰-/ level. The authors obtain the density of D⁰-/ states in a-Si,Ge:H,F which peak at E_c-(0.40 to 0.45) eV, with maxima in the 10¹⁸ to 10¹⁹ cm^-3eV^-1 range. In a-Si:H, the peak lies at E_c-0.45 eV; they observe its growth with increasing light-soaking time