Minority carrier properties of single- and polycrystalline silicon films formed by aluminium-induced crystallisation [solar cells]

The aluminium-induced crystallisation (AlC) of amorphous silicon is a simple low-temperature method for the growth of thin (/spl les/0.5 /spl mu/m), p-type (/spl sim/2/spl times/10/sup 18/ cm/sup -3/) single- and polycrystalline Si films on Si wafers and foreign substrates, respectively. While previous work has shown that such Si films can be used as thin emitters of p/sup +/-n Si wafer cells, this paper investigates the minority carrier diffusion length L/sub n/ of AlC-grown Si and thus determines whether these films can be used as absorber layer (i.e. base region) of c-Si solar cells. The AlC-grown Si films are made at 460/spl deg/C on single-crystal n-Si wafers and glass, respectively. By means of current-voltage and quantum efficiency measurements, the authors show that L/sub n/ in their AlC-grown p/sup +/-Si films is only about 100 nm. This is far too low to enable the use of these AlC films as absorber layers in thin-film c-Si solar cells. However, as shown in a companion paper (Harder et al.), these AlC films are excellent seeding layers on glass that can epitaxially be thickened by suitable Si deposition methods.