Surface band-bending effects on the optical properties of indium gallium nitride multiple quantum wells

We report the use of selective wavelength excitation to examine the surface band-bending effects on the optical properties of 3.0-nm-thick indium gallium nitride (InGaN) multiple quantum wells (MQWs). Under a 355-nm excitation, the In0.18Ga0.82N well emission exhibits a linear dependence on the injected carrier density (N-inj) with a coefficient of (i) 8.5x10(-18) meV cm(3) for the spectral blueshift and (ii) 3x10(-14) V cm(2) for the change of internal field at a density up to N(inj)similar to10(19) cm(-3) at 77 K. When excited by a shorter wavelength at 248 nm, the emission from the thin GaN cap layer quenches, but that from the InGaN wells prevails. These observations are attributed to the transportation of photogenerated carriers from the bent GaN surface and redistribution in the InGaN wells. By solving the rate and Poisson equations with a Fermi-level pinning in the band-structure analysis, the emission from the InGaN/GaN MQWs is shown dominant by the recombination between the high-lying subbands and the screening of internal field effects. (C) 2003 American Institute of Physics.