Uniformity and physical properties of semi-insulating Fe-doped InP after wafer or ingot annealing

Semi-insulating Fe-doped InP was annealed under different conditions and investigated by Hall effect, extrinsic photocurrent mapping, chemical etching, and optical microscopy. The resistivity is increased for any treatment, particularly in wafer-annealed InP. This result is probably due to strong losses of shallow donors. Remarkable differences exist between the structural properties of the wafer and ingot annealed material; wafer annealing produces a quick elimination of growth striations and decoration microdefects while ingot-annealed InP still retain these microdefects, both along dislocations and in the matrix. The photocurrent maps indicate that the thermal treatments normally improve the doping uniformity (especially the short-range fluctuations). The best uniformity is achieved for the long annealing time (greater than or equal to 50 h), while a slow cooling rate improves the mobility.