Guanghong Wang

In situ optical emission spectroscopy diagnostics of glow discharges in SiH4/GeH4/H2

An optical emission spectroscopic study identifies transient and steady-state behavior of the excited H*α/H*β/SiH*/GeH* emission in parallel plate SiH4/GeH4/H2 plasma. The effect of deposition parameters on the radical density in plasma is determined. To clarify the radical production mechanism further, the optoelectronic properties of the hydrogenated amorphous silicon–germanium thin films deposited at different hydrogen flow rates in 3 Torr pressure are investigated. The results show a low hydrogen flow rate improves the optoelectronic properties of the thin films whereas a high flow rate leads to a much higher defect density in the thin films. The ratio of GeH* to SiH* emission intensity is related to the germanium content in the plasma. The germanium content is changed for the different hydrogen flow rates, thereby adjusting the optical bandgap, with 1.32 ± 0.20 eV at a high 200 sccm hydrogen flow rate.

Improving surface passivation capability of silicon heterojunction solar cells with amorphous silicon by optical emission spectrometry

The intrinsic a-Si:H thin film is the key to the high efficiency heterojunction silicon solar cells. The transient instability after plasma ignition decreases the minority carrier lifetime of passivated silicon wafer at the same deposition process. The capability to passivate the silicon surface of a-Si:H thin films deposited at different hydrogen flow rate is investigated. The results show the passivation capability at higher hydrogen flow rate is poorer. The decrease of Hα*, Hβ* and SiH* emission intensity in plasma is not easier to passivate the silicon surface.