Electrical and structural characterization of MBE GaAs grown at temperatures between 200 and 600 °C

摘要

As-grown and annealed MBE GaAs layers prepared at various temperatures T_g=200-600 °C are analyzed and a strong influence of T_g on the layer properties is demonstrated. In as-grown layers the resistivity extremely increases, by six orders of magnitude, with T_g increased from 200 to 400 °C An opposite effect, a strong decrease of the resistivity occurs if T_g increases from 450 to 600 °C. Semi-insulating GaAs layers (ρ_(300)～10~7Ω cm) with regular GaAs lattice constant can be prepared at T_g between 400 and 450 °C without annealing and these layers are thermally stable in their resistivity during annealing (590 °C, 10 min). Photoconductors prepared on 400 °C layers show a higher sensitivity but a longer response time than on typical LTG GaAs layers. Further, the BEP ratio between 7 and 19 has no significant influence on the resistivity of 200 °C layers but for 350 °C grown layers an increase of the resistivity by factor of about 10 with decreasing BEP ratio is observed for both as-grown and annealed layers. Finally, we observed an influence of the annealing time on the resistivity of GaAs layers.