ABSTRACT
The effect of impurities and native point defects on hole transport in Culn1-xGaxSe2 (CIGS) epitaxial layers grown on GaAs are described in summary form. Single-crystal films with 0.03<x<1.00 have been characterized and the effects of Cu/(In+Ga) ratio, Na, and implants of Se, Cr, Al, Zn, and O were characterized. All films studied were p-type with p between 4×1016 and 2×1019 cm-3 at 300 K. Two acceptor levels and compensating donors were observed. Increasing Ga content increased acceptor density but not depth. The room temperature mobility behavior was unchanged by changes in film composition or Ga content over a wide range. Impurities studied also have little effect on mobility. Na was found to reduce compensation significantly leading to an apparent increase in hole concentration. Ion implantation of all species studied produced similar effects: a degradation in mobility and an increase in hole concentration. Se and Cr implant damage was mostly removed by annealing at 550°C for 25 min while Al, Zn, and O implant damage was more significant initially and remained generally unaffected by annealing. The difference between the higher (Cr and Se) and lower (Al, Zn, O) atomic mass implants may have been due to differences in resulting ion damage distributions or to small differences in implant doses.
