Carrier injection modulated by V-defects in InGaN/GaN multiple-quantum-well blue LEDs

Abstract

We investigated the carrier injection mechanism in InGaN/GaN blue light-emitting diodes by growing monolithic dual-wavelength multiple quantum wells and measuring electroluminescence spectra at different current densities at room temperature. During the epitaxial growth, V-defects of different sizes were intentionally formed in the active region area by controlling the growth conditions. We found that the size of the V-defects has a significant effect on the spectral competition of dual-wavelength emissions. With small V-defects, light emitted from quantum wells near p-GaN is dominant. In a sample with large V-defects, quantum wells near n-GaN contribute more to carrier recombination. The hole injection depth of eight pairs of quantum wells far from p-GaN is quantitatively estimated. We attribute the different behaviors to the modulation of carrier injection depth by the formed V-defects.

Electroluminescence from the InGaN/GaN Superlattices Interlayer of Yellow LEDs with Large V-Pits Grown on Si (111)

“…[1] The V-pits techniques have been developed to enhance performance of devices by promoting hole injection [2−4] and screening the dislocations. [5,6] Our previous work [7] and Li et al [8] reported that a number of holes could inject into multiple quantum wells (MQWs) through the sidewalls of large V-pits in addition to through the 𝑐-plane region, which is important for GaN LEDs. However, the specific hole transport process in the V-pits embedded LED structures is not very clear, so more in-depth research needs to be carried out.…”

“…If there are no V-pits, hole injection is only through the flat 𝑐-plane region (path 1) of the LED structure. In contrast, it is well known that holes could also inject via the sidewalls of V-pits (path 2) in the V-pit-embedded LEDs, [7,8] as shown in Fig. 5.…”

Performance improvement of ultraviolet-A multiple quantum wells using a vertical oriented nanoporous GaN underlayer

“…V-defects are present on the MQWs surface in the inset of figure 4(a), with an average size of about 180 nm and a density of 8 × 10 8 cm −2 . They is formed at the end of the threading dislocation (TD), which originates from the buffer GaN layer and extends to the MQWs along the direction of (0002) [21][22][23][24][25]. After EC etching, there is no obvious etched pore on the MQWs surface except for V-defects.…”

Effect of superlattice on light output power of InGaN‐based light‐emitting diodes fabricated on underlying GaN substrates with different dislocation densities

“…Some groups have proposed various mechanisms for improving the electroluminescence properties of LEDs by using V-pits in the active layer. Li et al confirmed that holes are injected into the deep portion of the light-emitting layer through the thin barrier layer of quantum wells in V-pits [6]. Hangleiter et al proposed a mechanism based on the "anti-localization" of charge carriers due to energy barriers arising from thin quantum wells in V-pits [7][8][9].…”