X-ray photoemission spectroscopy was used to measure directly the CdTe-HgTe (¯1¯1¯1) heterojunction valence-band discontinuity (${\Delta E}_v$) with the result ${\Delta E}_v=0.35\mathrm{}\pm 0.06$ eV. On the basis of the frequently applied common-anion rule, it has generally been assumed that ${\Delta E}_v$ would be small; the large value of ${\Delta E}_v$ will affect predicted CdTe-HgTe heterojunction and superlattice properties. In conjunction with recent ${\Delta E}_v$ measurements on the $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}-{\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ heterojunction system, the large ${\Delta E}_v$ result for the CdTe-HgTe (¯1¯1¯1) heterojunction provides direct experimental evidence in contradiction to the common-anion rule for lattice-matched heterojunction interfaces.

• Received 7 January 1986

DOI:https://doi.org/10.1103/PhysRevLett.56.1605