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

Abstract

The minority carrier lifetime of electrons ${\mathrm{(\tau }}_n)$ in $p$ -type GaAs double heterostructures grown on GaAs substrates and compositionally graded ${\mathrm{Ge/Si}}_{\text{1−x}}{\mathrm{Ge}}_x/\mathrm{Si}$ (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 $(\mathrm{TDD}{\text{∼1×10}}^6\hspace{0.17em}{\mathrm{cm}}^{\text{−2}})$ with a dopant concentration of ${\text{2×10}}^{17}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ were $\text{∼21}$ and $\text{∼1.5\hspace{0.17em}}\mathrm{ns},$ respectively. The electron lifetime measured on SiGe was substantially lower than the previously measured minority carrier hole lifetime ${\mathrm{(\tau }}_p)$ of $\text{∼10\hspace{0.17em}}\mathrm{ns},$ 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.