Characteristics of CuGaSe₂ layers grown on GaAs substrates

CuGaSe₂ films are grown on GaAs (001) substrates by migration-enhanced epitaxy. Electron probe X-ray micro analysis measurement shows that the CuGaSe₂ films are stoichiometric regardless of the Cu/Ga supply ratio, which indicates that migration-enhanced epitaxy is useful for making stoichio-metric CuGaSe₂ films. Hall effect measurement indicates the p-type conductivity with the hole mobility as high as 2700 cm ²/Vs at low temperatures. The photoluminescence spectrum at 4 K is dominated by the band-edge emission which includes both A-band free and bound exciton emissions. The emission due to donor-acceptor pairs and other deep levels are observed very weakly. Moreover, at temperatures above 180 K, a new emission band appears in the higher energy region of the band-edge emissions. The peak is tentatively attributed to the emission including the B-band free exciton. These results indicate that the optical properties of the CuGaSe ₂ films grown by using migration-enhanced epitaxy are fairly good.