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

A line at $E$ = 2.77 eV (with a width of $\Gamma$ = 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 $E_{1}$ = 2.55 eV and $E_{2}$ = 2.75 eV and widths of $\Gamma_1$ = 66 meV and $\Gamma_2$ = 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 $E_{1}$ and $E_{2}$ 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.