Interface strain in InGaAs-InP superlattices

We have studied the strain in OMVPE grown ultra thin As compound layers in InP and P-compound layers in GaAs to assess interface behavior relevant to InGaAs/InP heterojunctions. Strain contributions from As-P exchange at the heterojunction interfaces were identified. The very rapid replacement of P by As from AsH₃ and the slower replacement of As by P from PH₃ results in a rapidly formed strain contribution from InAs rich interfaces for superlattices on InP substrates. An additional InAs-like strain in the inserted layers is proportional to the growth time and is attributed to carryover at the upper interface of excess adsorbed surface As into the InP overlayer. P interaction with As-compounds is sufficiently slow that excess negative strain occurs only when deliberate growth interrupts under PH₃ are introduced into superlattices grown on GaAs substrates, and P incorporation behaves more like diffusion into the underlying GaAs rather than as P carryover into the GaAs overlayer. Under our normal growth conditions, growth of thin GaP-compound layers on GaAs incorporates residual As at an exact 50% As-50% P ratio