Reduction of Efficiency Droop in Semipolar (1\bar101) InGaN/GaN Light Emitting Diodes Grown on Patterned Silicon Substrates

Abstract

We present a study of semi-polar (1101) InGaN-based light emitting diodes (LEDs) grown on patterned (001) Si substrates by atmospheric-pressure metal organic chemical vapor deposition. A transmission electron microscopy image of the semi-polar template shows that the threading dislocation density was decreased significantly. From electroluminescence measurement, semi-polar LEDs exhibit little blue-shift and low efficiency droop at a high injection current because the reduction of the polarization field not only made the band diagram smoother but also restricted electron overflow to the p-GaN layer as shown in simulations. These results indicate that semi-polar InGaN-based LEDs can possess a high radiative recombination rate and low efficiency droop at a high injection current.

Efficiency droop in light‐emitting diodes: Challenges and countermeasures

“…Nevertheless, there have been successful efforts to reduce or overcome efficiency droop in GaN‐based LEDs grown on c‐plane sapphire substrates, which include: (i) reducing the carrier density by employment of wide QWs or LED chips with large area , (ii) reducing the electron leakage by modification of MQW structures and EBL structures , and (iii) polarization‐engineered MQW and EBL structures . LEDs grown in the m‐plane, a‐plane, and other non‐polar or semi‐polar planes of the wurtzite crystal have been topics of active research to reduce efficiency droop . These designs inherently have a lower polarization mismatch than the conventional c ‐plane polar LEDs that are universal in industry.…”

Semi‐polar ‐GaN templates grown on 100 mm trench‐patterned r‐plane sapphire

“…Since non‐ c ‐plane GaN substrates are limited in size and availability, the need for low‐cost large diameter non‐ or semi‐polar templates is apparent. To circumvent the substrate dilemma, different heteroepitaxial approaches both on sapphire and silicon have been proposed.While direct growth of non‐ or semi‐polar GaN on planar sapphire is hampered by the incorporation of extended defects like basal plane stacking faults and partial dislocations , the use of patterned substrates is promising. Here, the inclined growth in c ‐direction on the sidewall of trench‐patterned substrates is particularly beneficial .…”

Catalyst‐Free GaN Nanorods Synthesized by Selective Area Growth

“…The large surface area of the active region can effectively decrease the operating current density hence alleviating the droop effect. In addition, the elimination of piezoelectric field inside the QWs on the non‐polar sidewalls allows a thicker quantum well to be formed and in turn reduces the leakage current and increases the radiative recombination efficiency . In order to form a uniform and reproducible nanorod array for high quality LED devices, it is important to find an adequate epitaxial method for their growth and to understand the physical mechanisms underlying their formation.…”