Secondary electron dopant contrast imaging of compound semiconductor junctions.

Secondary electron imaging combined with immersion lens and through-the-lens detection has been used to analyze various semiconductor junctions. Dopant contrast imaging was applied for multi-doped 4H-SiC, growth-interrupted n+/p and n/n+ homoepitaxial interfaces, and an AlGaAs/GaAs p-n junction light-emitting diode structure. Dopant contrast was explained by the local variation in secondary electron escape energies resulting from the built-in potential difference. The effect of varying electron affinity on contrast for the heterostructures is also discussed. The contrast profile of the n-doped AlGaAs compared reasonably well to the simulated valence bandedge energy using a previously determined efficiency of dopant ionization. [ABSTRACT FROM AUTHOR]