 using a scanning tunneling and atomic 
 force microscope combined with in - vacuum atomic hydrogen cleaning 
 we demonstrate stable scanning tunneling spectroscopy ( sts ) with nanoscale 
 resolution on electrically active nanowire devices in the common lateral 
 configuration . 
 we use this method to map out the surface density of 
 states on both the gasb and inas segments of gasb  inas esaki 
 diodes as well as the transition region between the two segments . 
 
 generally the surface shows small bandgaps centered around the fermi 
 level , which is attributed to a thin multielement surface layer , except 
 in the diode transition region where we observe a sudden broadening 
 of the bandgap . by applying a bias to the nanowire 
 we find that the 
 sts spectra shift according to the local nanoscale potential drop 
 inside the wire . 
 importantly , this shows that we have a nanoscale 
 probe with which we can infer both surface electronic structure and 
 the local potential inside the nanowire and we can connect this information 
 directly to the performance of the imaged device . 
Supplementary Material