Impact of dislocations on minority carrier electron and hole lifetimes in GaAs grown on metamorphic SiGe substrates

The minority carrier lifetime of electrons (tau(n)) in p-type GaAs double heterostructures grown on GaAs substrates and compositionally graded Ge/Si1-xGex/Si (SiGe) substrates with varying threading dislocation densities (TDDs) were measured at room temperature using time-resolved photoluminescence. The electron lifetimes for homoepitaxial GaAs and GaAs grown on SiGe (TDDsimilar to1x10(6) cm(-2)) with a dopant concentration of 2x10(17) cm(-3) were similar to21 and similar to1.5 ns, respectively. The electron lifetime measured on SiGe was substantially lower than the previously measured minority carrier hole lifetime (tau(p)) of similar to10 ns, for n-type GaAs grown on SiGe substrates with a similar residual TDD and dopant concentration. The reduced lifetime for electrons is a consequence of their higher mobility, which yields an increased sensitivity to the presence of dislocations in GaAs grown on metamorphic buffers. The disparity in dislocation sensitivity for electron and hole recombination has significant implications for metamorphic III-V devices. (C) 2004 American Institute of Physics.