(a) (b) Ec(z) Ev(z) PARABOLIC WELL E6h 38 E'7h I 0 Esh E4h E3h E 3Sh E 24 h i 46 10 1.56 72 172 PHOTON ENERGY (evi FIGURE 4.5. (a) Parabolic potential in both conduction and valence bands grown into GaAs by a graded composition of AIX Gal _x As. The band gap has been reduced in this sketch, and only heavy holes are shown. (b) Photoluminescence in parabolic wells. [From Miller et al. (1984).]