DISLOCATION IMAGING OF AN INALGAAS OPTOELECTRONIC MODULATOR USING IBICC

This paper presents Ion Beam Induced Charge Collection (IBICC) contras t images showing regions of differing charge collection efficiency wit hin 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 differ ent {110} directions which correlate with misfit dislocations within t he 392 nm thick strained-layer superlattice quantum well of the modula tor structure. Independent cross-sectional TEM studies and the electri cal properties of the devices under investigation suggest the presence of threading dislocations in the active device region at a density of less than or similar to 10(6) cm(-2). However, no clear evidence of t hreading dislocations was observed in the IBICC images as they are pos sibly masked by the strong contrast of the misfit dislocations. Charge carrier transport within the modulator is used to explain the observe d contrast. The different signal to noise levels and rates of damage o f the incident ions are assessed. (C) 1997 Elsevier Science B.V.