A passivation scheme, featuring nanocomposite amorphous silicon suboxides (a-SiOx:H) is investigated and analyzed in this work. The a-SiOx:H films are deposited by high-frequency plasma-enhanced chemical-vapor deposition via decomposition of silane (SiH4), carbon dioxide (CO2), and hydrogen (H2) as source gases. The plasma deposition parameters of a-SiOx:H films are optimized in terms of effective lifetime, while the oxygen content and the resulting optical band gap EG of the a-SiOx:H films are controlled by varying the CO2 partial pressure χO=[CO2]/([CO2]+[SiH4]). Postannealing at low temperatures of those films shows a beneficial effect in form of a drastic increase of the effective lifetime. This improvement of the passivation quality by low temperature annealing for the a-SiOx:H likely originates from defect reduction of the film close to the interface. Raman spectra reveal the existence of Si–(OH)x and Si–O–Si bonds after thermal annealing of the layers, leading to a higher effective lifetime, as it reduces the defect absorption of the suboxides. The surface passivation quality of a-SiOx:H within both n-type and p-type silicon has been studied as a function of injection level. Record high effective lifetime values of 4.7 ms on 1 Ω cm n-type float zone (FZ) wafers and 14.2 ms on 130 Ω cm p-type FZ wafers prove the applicability for a surface passivation of silicon wafers applicable to any kind of silicon-based solar cells. The effective lifetime values achieved on a highly doped crystalline wafer (1 Ω cm resistivity) appears to be the highest value ever reported. Samples prepared in this way feature a high quality passivation yielding effective lifetime values exceeding those of record SiO2 and SiNx passivation schemes.

In this letter, we report on our investigations of hydrogenated amorphous silicon suboxides (a-SiOx:H) used as a high quality passivation scheme for heterojunction solar cells. The a-SiOx:H films were deposited using high frequency (70MHz) plasma enhanced chemical vapor deposition by decomposition of carbon dioxide, hydrogen, and silane at a substrate temperature of around 155°C. High effective lifetimes of outstanding 4ms on 1Ωcm n-type float-zone material and a surface recombination velocity of ⩽2.6cm∕s have been repeatedly obtained. Optical analysis revealed a distinct decrease of blue light absorption in the a-SiOx:H films compared to commonly used intrinsic amorphous silicon passivation used in heterojunction cells.

Temperature dependent resistivity and Hall measurements have been carried out on in situ boron doped polycrystalline diamond films. The temperature dependence of the resistivity can be described by a two band conduction model with two conduction mechanisms working parallel. A fair agreement between the depth distribution of the boron concentration determined from spreading resistance and secondary ion mass spectroscopy is found. Room temperature resistivities and activation energies from various sources are compared with the present work. With the aid of these curves the doping and hole concentrations can be estimated from room temperature resistivity measurements. ~ I )

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Tunnel injection and irradiation experiments on metal oxide semiconductor (MOS) structures are performed in order to compare the results of both experiments and to check the feasibility of radiation hardness prediction of MOS devices. The comparison is based on the fact that in both hot electron and ionizing irradiation experiments electron-hole pairs are generated in the SiO2. Due to an applied electrical field, these pairs are separated. The fraction of holes, trapped by neutral centers and the number of subsequently captured electrons by these now positively charged traps depend on the amount of available carriers, the magnitude of the respective capture cross sections for electrons and holes, and the number of hole traps. In the case of the tunnel injection experiment the number of the available carriers is a strong function of the field dependent ionization coefficient α. Up to now, its magnitude has not been accurately known. For this reason, a new method is presented which yields additional and reliable figures of α. When comparing the charge accumulation in the SiO2 by means of the flatband voltage shift as a consequence of the tunnel injection and of the irradiation, we determine α for various fields, α=3.3×10−6 exp [78/E(MV/cm)] (cm−1). For this determination we show that it is mandatory to correct for the steady state compensation of positively charged centers by electrons. From the saturation of the flatband voltage shift, caused by these trapped electrons, the field dependent capture cross sections for electrons are deduced. Their values are 2.3×10−14 and 3.5×10−15 cm2 for electrical fields of 7.8 and 8.6 MV/cm, respectively. The feasibility and limitations to predict the radiation hardness of MOS devices are discussed.