InGaAs/InP quantum well intermixing studied by cross-sectional scanning tunneling microscopy

Cross-sectional scanning tunneling microscopy (STM) is used to study lattic e matched InGaAs/InP quantum well (QW) intermixing induced by ion implantat ion and thermal annealing. Different strain development in QWs (determined by STM topography of elastic relaxation in cross sectionally cleaved sample s) is found to be dependent upon the range of the implanted ions relative t o the QWs. It is found that the quantum wells remain latticed matched to th e barrier layers after intermixing when ions are implanted through the mult iple quantum well (MQW) stack. A shallow implantation in which ions are imp lanted into the cap layer above the MQW stack leads to tensilely strained w ells and compressively strained interfaces between wells and barriers. The strain development in the latter case is attributed to different degrees of interdiffusion on the group III and group V sublattices. Finite element el astic computations are used to extract the group V and group III interdiffu sion length ratio, and results using different diffusion models are compare d. A preferred group V interdiffusion in the case of shallow implantation i s explained in terms of faster diffusing P related defects compared to In r elated defects. Images of as-grown QWs provide useful information about the growth technique related compositional fluctuations at the interfaces. (C) 2001 American Institute of Physics.