ER LUMINESCENCE-CENTERS IN GAAS GROWN BY MIGRATION-ENHANCED EPITAXY

Er-doped GaAs has been grown by migration-enhanced epitaxy. The sample s were grown at 300, 400, and 500-degrees-C. Secondary ion mass spectr oscopy measurements showed that the Er concentration in the grown epit axial layer does not depend on the growth temperature between 300 and 500-degrees-C. All samples showed luminescence due to the Er intra-4f- shell transition from the I-4(13/2) excited state to the I-4(15/2) gro und state, but the spectra change drastically when the growth temperat ure is increased from 300-degrees-C to 400 or 500-degrees-C. The photo luminescence spectra of the samples grown above 400-degrees-C are simp ler than that of the sample grown at 300-degrees-C. The spectrum of th e sample grown at 300-degrees-C became broad after annealing, whereas the spectra of the samples grown at 400-degrees-C and above showed onl y changes in the relative intensity of the main luminescence lines. So me thermally stable Er luminescence centers seem to be preferentially formed at 400 and 500-degrees-C.