AsH 3 to Ga(CH 3 ) 3 Mole Ratio Dependence of Dominant Deep Levels in MOCVD GaAs

Dependence of the 0.8 eV electron trap (so-called EL2) concentration on the As/Ga mole ratio during growth in MOCVD GaAs has been investigated by varying growth temperatures. It has been found that a demarcation exists in the growth temperatures, which divides two regions with different trap concentration-As/Ga mole ratio relationships. The trap concentration increases with the As/Ga mole ratio by the one-fourth power at growth temperatures of 630°C and 660°C, while it increases with the As/Ga mole ratio by the one-half power at 720°C and 740°C. Corresponding with this difference, there is a slight difference in activation energies between the materials grown at the lower temperatures and those grown at the higher temperatures. A possible explanation based on thermodynamic considerations is presented.