Dislocation imaging of an InAlGaAs opto-electronic modulator using IBICC

This paper presents ion beam induced charge collection (IBICC) contrast images showing regions of differing charge collection efficiency within optoelectronic modulator devices. The experiments were carried out at the Sandia nuclear microprobe using 18 MeV carbon and 2 MeV helium ions. Lines of varying densities are observed to run along the different {l_brace}110{r_brace} directions which correlate with misfit dislocations within the 392nm thick strained layer superlattice quantum well of the modulator structure. Independent cross-sectional TEM studies and the electrical properties of the devices under investigation suggest the presence of threading dislocations in the active device region at a density of {approximately} 10{sup 6} cm{sup {minus}2}. However, no clear evidence of threading dislocations was observed in the IBICC images as they are possibly masked by the strong contrast of the misfit dislocations. Charge carrier transport within the modulator is used to explain the observed contrast. The different signal to noise levels and rates of damage of the incident ions are assessed