Characterisation of defects and piezoelectric fields in InGaN/GaN layers by transmission electron microscopy

Transmission electron microscopy is used to examine the microstructure of high quality hexagonal InGaN/GaN layers grown by MOCVD. It is shown that a combination of imaging and convergent beam diffraction techniques gives information on the types of threading dislocation present, and on the structure of nanopipes, inversion domains and inversion domain boundaries. Recent results which throw new light on the nanopipe formation mechanism are also reported. We also present preliminary work in which electron holography has been used to investigate piezoelectric fields generated across strained InGaN quantum wells.