Investigation of defect formation and electronic transport in microcrystalline silicon deposited by hot-wire CVD

Abstract

Abstract:We have investigated doped and undoped layers of microcrystalline silicon prepared by hot wire chemical vapour deposition optically, electrically and by means of transmission electron microscopy. Beside needlelike crystals grown perpendicular to the substrate's surface all of the layers contained a noncrystalline phase with a volume fraction between 4% and 25%. A high oxygen content of several per cent in the porous phase was detected by electron energy loss spectrometry. Deep level transient spectroscopy of the crystals suggests that the concentration of electrically active defects is less than 1% of the undoped background concentration of typically 10 17 cm -3 . Frequency dependent measurements of the conductance and capacitance perpendicular to the substrate surface showed that a hopping process takes place within the noncrystalline phase parallel to the conduction in the crystals. The parasitic contribution to the electrical circuit arising from the porous phase is believed to be an important loss mechanism in the output of a pin-structured photovoltaic solar cell deposited by hot wire CVD.

Kelvin probe measurements of microcrystalline silicon on a nanometer scale using SFM

“…Frequency dependent capacitance−voltage and conductance−voltage measurements confirmed that the DLTS measurements provided information on defects in the crystalline phase [3]. DLTS measurements on undoped µc−Si/ZnO rectifying Schottky diode structures revealed three easily resolvable donors with activation energies of 0.027eV, 0.185eV potentially induced by interstitial Cu + and 0.336eV which may be attributed to tungsten from the hot filament.…”

“…One acceptor with an activation energy of 0.104eV could be resolved. DLTS on pin diodes revealed three more shallow donor levels with activation energies lower than 0.140eV attributed to oxygen [3]. Despite the presence of a noncrystalline phase usually causing defect induced band tails as observed by optical absorption measurements distinct defect levels could be measured by DLTS typical for crystalline material.…”

“…A defect distribution known from amorphous silicon (dangling bonds, band tails) would yield a similar shape of the surface potential. But due to the relatively low measurement frequency the crystalline phase plays the dominant role in nanopotentiometry [3].…”

Charge transport in hydrogenated boron-doped nanocrystalline silicon-silicon carbide alloys

“…At the same time, the doping level may influence the degree of the structural disorder, film crystallinity, and defect density distribution. Various carrier transport mechanisms have been reported for a-Si: H, 9-11 c-Si: H, 12,13 and nc-C:H films. 14 In this paper, we investigated the electric transport of p-nc-Si− SiC: H alloys.…”

Tem Study of The Microstructure of Si Thin Films Deposited by Hot Wire CVD

“…Improved understanding of these mechanisms may afford a better control of the deposition process and yield a higher performance devices. Furthermore, little has been reported on the structural and morphological properties of such films 1,2,3 .…”