Staggered-lineup heterojunctions as sources of tunable below-gap radiation: Experimental verification

We report experimental verification of the prediction of widely bias-tunable below-gap luminescence, from lattice-matched (p) (Al,In)As/ (n) InP heterojunctions, a system that has been predicted to have staggered lineup. The diodes, grown by molecular beam epitaxy, exhibit strong luminescence at 1.4 K, with a peak energy that shifts from 0.97 to 1.04 eV as the (pulsed) current density is increased from 4.5 to 40 A/cm2. Nonshifting injection luminescence at 1.4 eV, due to hole injection into the n-InP substrate, was also present, but appreciably weaker (<25%) than the interface luminescence. The spectra indicate that the band lineup in the (Al,In)As/InP system is indeed staggered, with a residual gap at the interface close to 0.96 eV. The corresponding conduction and valence-band offsets are 0.52 and 0.40 eV.