A Pathway to Low-Shift Red LEDs: Bulk InGaN as the Active Region

Strained InGaN quantum wells (QWs) are commonly used as the active region for red light-emitting diodes (LEDs). However, the strong polarization field in red QWs leads to a significant wavelength blueshift with increasing current injection. In this study, red InGaN LEDs with minor blueshift were achieved using a bulk InGaN active region. As the current density increased from 0.04 to 80 A/cm 2, the peak wavelength shifted only by 7.5 nm, in the range of 623.0–615.5 nm. In this approach, the compressive stress in bulk InGaN was relaxed by high-density trench structures. In the strain-relaxed state, bulk InGaN exhibited phase separation, forming low-In-content (blue) and high-In-content (red) phases. The red phase acted as carrier localization centers, emitting red light under electrical injection. The minor blueshift of red LEDs can be attributed to the negligible polarization electric field in the red phase. This study presents an approach for achieving low-shift red InGaN LEDs.