The interfaces of a lattice‐matched InP/InGaAs double‐barrier resonant tunneling diode are studied by scanning tunneling microscopy. The interfaces have been mapped with atomic resolution for a length of over 4000 A, and scanning tunneling microscopy images show the roughness to be very asymmetric with the inverted (InP on InGaAs) interface being considerably rougher than the normal interface. Roughness wave vectors determined from Fourier analysis are well fitted by a Lorentzian function and allow determination of roughness amplitudes and correlation lengths for the different interfaces. A chemical asymmetry between the interfaces is also observed in certain images which exhibit enhanced and reduced state densities at the normal and inverted interfaces, respectively. Termination of the growth surface by differing column V species during interface formation most likely affects the local state density.