Quantitative and Depth-Resolved Investigation of Deep-Level Defects in InGaN/GaN Heterostructures

Deep-level defects in In_0.17Ga_0.83N/In_0.02Ga_0.98N/p-GaN:Mg heterostructures were studied using deep-level optical spectroscopy (DLOS). Depth-resolved DLOS was achieved by exploiting the polarization-induced electric fields to discriminate among defects located in the In_0.17Ga_0.83N and the In_0.02Ga_0.98N regions. Growth conditions for the In _x Ga_1−x N layers were nominally the same as those in InGaN/GaN multi-quantum-well (MQW) structures, so the defect states reported here are expected to be active in MQW regions. Thus, this work provides important insight into defects that are likely to influence MQW radiative efficiency. In_0.17Ga_0.83N-related bandgap states were observed at E _v + 1.60 eV and E _v + 2.59 eV, where E _v is the valence-band maximum, compared with levels at E _v + 1.85 eV, E _v + 2.51 eV, and E _v + 3.30 eV in the In_0.02Ga_0.98N region. A lighted capacitance–voltage technique was used to determine the areal density of deep states. The possible origins of the associated defects are considered along with their potential roles in light-emitting diodes.