ELECTRONIC STATES IN GRADED-GAP JUNCTIONS WITH BAND INVERSION

We theoretically study electronic states in graded-gap junctions of IV-VI compounds with band inversion. Using a two-band model within the ${\bf k}\cdot{\bf p}$ approximation and assuming that the gap and the gap centre present linear profiles, we demonstrate the existence of a set of localized states along the growth direction with a discrete energy spectrum. The envelope functions are found to be combination of harmonic oscillator eigenfunctions, and the corresponding energy levels are proportional to the square root of the quantum number. The level spacing can be directly controlled by varying the structure thickness.