Electroreflectance spectra from multiple InGaN/GaN quantum wells in the nonuniform electric field of a p–n junction

Abstract

A line at E = 2.77 eV (with a width of Γ = 88 meV) related to interband transitions in the region of multiple quantum wells in the active region is detected in the electroreflectance spectra of the GaN/InGaN/AlGaN heterostructure. As the modulation bias is reduced from 2.9 to 0.4 V, the above line is split into two lines with energies of E₁ = 2.55 eV and E₂ = 2.75 eV and widths of Γ₁ = 66 meV and Γ₂ = 74 meV, respectively. The smaller widths of separate lines indicate that these lines are caused by interband transitions in particular quantum wells within the active region. The difference between the interband transition energies E₁ and E₂ in identical quantum wells in the active region is related to the fact that the quantum wells are in an inhomogeneous electric field of the p–n junction. The magnitudes of the electric-field strengths in particular quantum wells in the active region of the heterostructure are estimated to be 1.6 and 2.2 MV/cm.