SCANNING TUNNELING MICROSCOPY SPECTROSCOPY STUDY OF SELF-ORGANIZED QUANTUM-DOT STRUCTURES FORMED IN GAP/INP SHORT-PERIOD SUPERLATTICES/

Self-organized quantum dot (QD) structures formed in (GaP)(n)(InP)(n) short-period superlattices (SLs) grown on GaAs (N11) substrates by gas source MBE (molecular beam epitaxy) are studied by scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS). STM images sh ow high density QD structures as bright areas. The dot size of these s tructures ranges from 15 nm to 25 nm with a dispersion of +/-10% depen ding on the n and m of the SLs. In the STS measurement, the voltage wi dth for dI/dV = 0 varies along the lateral direction on the sample sur face. This voltage width variation corresponds to the lateral variatio n of the band-gap energy and of the tunneling probability by the later al composition modulation.