Optical Properties of n-Type GaAs. III. Relative Band-Edge Recombination Efficiency of Si- and Te-Doped Crystals before and after Heat Treatment

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Abstract
A study of the effect of annealing upon the efficiency of edge emission in heavily Si‐doped GaAs crystals reveals a substantially different behavior from that observed in Te‐doped GaAs crystals of comparable doping level. Essentially no change in the edge emission intensity at 77°K and a decrease of only a factor of two at 300°K is found for GaAs:Si after annealing in contrast to a decrease of a factor of 10 at 77°K and a factor of five at 300°K for GaAs:Te. The intensity of the 1.2‐eV band in GaAs:Si decreases after annealing while the same band increases in intensity in GaAs:Te. From the hole diffusion length and hole lifetime analysis, it is concluded that annealing GaAs:Si reduces SiVGa (Si‐donor‐Ga‐vacancy complex) centers but at the same time creates other unknown defects, both of which have smaller concentrations than some other compensating acceptors. These compensating acceptors are shown to be present only in GaAs:Si and are presumably Si acceptors. It is also demonstrated that the hole capture rates at SiVGa acceptors, at defects created during annealing, and at the compensating acceptors are all competitive in GaAs:Si after annealing, but only the hole capture rate at TeVGa is important in GaAs:Te. Although the 77°K hole lifetime is smaller for unannealed GaAs:Si than for GaAs:Te, the 77°K edge emission efficiency is approximately the same for both dopants if the crystals have the same room temperature carrier concentration. This result is due to the less steep absorption edge of Si‐doped crystals and the shift of the absorption edge to the lower energy. Similar behavior is also found for the 300°K case and is mainly due to the less steep absorption edge of GaAs:Si.