A hole accelerator for InGaN/GaN light-emitting diodes

Abstract

The quantum efficiency of InGaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, and this is caused by the inefficient p-type doping and the low hole mobility. The low hole mobility makes the holes less energetic, which hinders the hole injection into the multiple quantum wells (MQWs) especially when a p-type AlGaN electron blocking layer (EBL) is adopted. In this work, we report a hole accelerator to accelerate the holes so that the holes can obtain adequate kinetic energy, travel across the p-type EBL, and then enter the MQWs more efficiently and smoothly. In addition to the numerical study, the effectiveness of the hole accelerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED. © 2014 AIP Publishing LLC

Numerical Investigations on the n+‐GaN/AlGaN/p+‐GaN Tunnel Junction for III‐Nitride UV Light‐Emitting Diodes

“…The band offset ratios (Δ E C /Δ E V ) of 70:30 and 50:50 for InGaN/GaN quantum wells and GaN/AlGaN heterojuntions are employed, respectively . We also take the polarization induced charges at the polarization‐mismatched interfaces along the [0001] oriented LED structure into consideration, and the polarization level is set to 40% . Other parameters of III‐nitride based semiconductors can be found elsewhere .…”

A hole modulator for InGaN/GaN light-emitting diodes

“…On one hand, the p-GaN material features a low hole mobility and the low hole mobility, in turn, reflects a less kinetic energy of holes, which leads to the low hole injection efficiency into the InGaN/GaN multiple quantum wells (MQWs). 3 Thus, various proposals have been reported in improving the hole transport within the InGaN/ GaN MQWs and enhancing the device efficiency including properly thinning the quantum barriers 4 and quantum wells, 5 using Mg-doped quantum barriers, 6,7 adopting tunneljunction cascaded active region, 8 as well as applying the InGaN quantum barriers. 9 On the other hand, the InGaN/ GaN LEDs are also impacted by the very low p-type doping efficiency.…”

Influence of an Insulator Layer on the Charge Transport in a Metal/Insulator/n‐AlGaN Structure

“…However, after inserting the insulator layer, we can clearly see from Figure (c) and (d) that the level of the metal affinity is above the conduction band of the n‐AlGaN layer, and hence the electrons have no barrier to climb over. Instead, the electrons are accelerated by gaining the 2.2 eV energy (i.e., Ф 1 in Figure (c) and Ф 4 in Figure (d) are both 2.2 eV), and the electrons can tunnel through the 1 nm thick insulator layer. Comparison between Figure (c) and (d) illustrates that the bandgap of the insulator does not affect the electron injection, since the electron injection by thermionic emission across the insulator is negligible.…”