Properties of Amorphous Hydrogenated Silicon Heterojunctions with Other Crystalline Semiconductors and Their Applications.

Amorphous hydrogenated silicon (ASIL) heterojunctions with other crystalline semiconductors have received considerable attention in recent years because of their application in many fields. The aims of this thesis were to investigate the characteristics of ASIL heterojunctions with several other crystalline (or polycrystalline) semiconductors, to study the preparation and fabrication techniques to reduce interface states, and to measure the junction properties and study the band offsets. Sample preparation processes were described for several ASIL heterojunctions, including pc-n:CuInSe _2/p:ASIL, pc-p:CuInSe_2/n:ASIL,c -n: i/p:ASIL,c-p:InP/n:ASIL & pc-n:CdSe/p:ASIL heterojunctions. The current voltage (I-V) and capacitance-voltage (C-V) measurements indicated that relatively abrupt heterojunctions were formed. From the analysis of the I-V characteristics at different temperatures and of C^2-V, the carrier transport mechanisms were obtained. Processes of multitunneling capture-emission and space-charge effects were involved in the forward I-V characteristics at low & high positive biases respectively. A generation current was involved in the reverse current. An internal optical excitation method was used to measure the energy band discontinuities at interfaces of pc-p:CuInSe_2/n:ASIL, c-n:Si/p:ASIL, c-p:InP/n:ASIL & pc-n:CdSe/p:ASIL heterojunctions. Electroluminescence (EL) of a pc-n:CuInSe_2/p{: }ASIL heterojunctions was measured, & the EL spectra indicated that the peak energy is 1.31 eV at 77 ^circK, which confirm that the EL signal is from the ASIL layer. Photoluminescence (PL) of a pc-n:CdSe/p:ASIL heterojunctions also was measured, and the PL spectra indicated the PL signal is from the ASIL layer. Threshold switches of In/pc-p:CuInSe_2 /n:ASIL/Al and Al/c-p^+{: }Si/c-p:Si/n:ASIL/Al were fabricated. The detailed carrier transport processes of the threshold switches were given. Solar cells of c-p:InP/n:ASIL & pc-n:CdSe/p:ASIL heterojunctions were also produced. The best efficiencies of cells of c-p:InP/n:ASIL & pc-n:CdSe/p:ASIL were 9.0% & 6.7% respectively. (These results could be improved by a sustained optimisation program).