Despite a high dislocation density and a strong polarization effect, during the past two decades, Gallium Nitride (GaN) based Light Emitting Diodes (LEDs) have emerged as solid state light sources in the spectral range from visible to ultraviolet. InGaN/GaN based Multiple Quantum Wells (MQWs) are employed as active layers in GaN based LEDs. It is well known that due to the lack of native substrates, GaN based devices are usually grown heteroepitaxially on substrates such as sapphire, resulting in a high density of Threading Dislocations (TDs) (~108 cm-2 – 109 cm-2) which traverse vertically from the substrate to the epilayer surface1. In addition, the surface defects such as V shaped defects and trench defects2,3 have also been observed in InGaN QW structures grown by Metal Organic Vapor Phase Epitaxy (MOVPE). These defects as a whole have a deleterious impact on the performance of LED Devices4,5. In earlier studies it was believed that the dislocations do not contribute to the electronic states of GaN and are electrically inert6,7. Recent findings have shown that the TDs can be optically and electrically active8. It is also reported that screw and mixed TDs act as non radiative recombination centres while the edge TDs are optically inert9. However, the effects of these defects on the electrical and optical properties of LED devices are still not fully understood. In this paper, we investigated a GaN based blue LED structure, containing a high density of dislocations, in order to get information about the effect of these dislocations on the micro structural, electronic and optical behaviours of these LEDs. The present work reports on the characterization of InGaN/GaN based LED structures by Atomic Force Microscope (AFM), which aimed at the detailed study of surface morphology and defect structures. The electrical properties of defects were studied by Electron Beam Induced Current (EBIC) and the luminescence properties of these LEDs were studied by Electroluminescence (EL).
Geeta Rani Mutta, Giulia Venturi, Antonio Castaldini, Anna Cavallini, Matteo Meneghini, Enrico Zanoni, et al. (2014). Microscopic, electrical and optical studies on InGaN/GaN quantum wells based LED devices [10.1063/1.4865660].
Microscopic, electrical and optical studies on InGaN/GaN quantum wells based LED devices
CASTALDINI, ANTONIO;CAVALLINI, ANNA;
2014
Abstract
Despite a high dislocation density and a strong polarization effect, during the past two decades, Gallium Nitride (GaN) based Light Emitting Diodes (LEDs) have emerged as solid state light sources in the spectral range from visible to ultraviolet. InGaN/GaN based Multiple Quantum Wells (MQWs) are employed as active layers in GaN based LEDs. It is well known that due to the lack of native substrates, GaN based devices are usually grown heteroepitaxially on substrates such as sapphire, resulting in a high density of Threading Dislocations (TDs) (~108 cm-2 – 109 cm-2) which traverse vertically from the substrate to the epilayer surface1. In addition, the surface defects such as V shaped defects and trench defects2,3 have also been observed in InGaN QW structures grown by Metal Organic Vapor Phase Epitaxy (MOVPE). These defects as a whole have a deleterious impact on the performance of LED Devices4,5. In earlier studies it was believed that the dislocations do not contribute to the electronic states of GaN and are electrically inert6,7. Recent findings have shown that the TDs can be optically and electrically active8. It is also reported that screw and mixed TDs act as non radiative recombination centres while the edge TDs are optically inert9. However, the effects of these defects on the electrical and optical properties of LED devices are still not fully understood. In this paper, we investigated a GaN based blue LED structure, containing a high density of dislocations, in order to get information about the effect of these dislocations on the micro structural, electronic and optical behaviours of these LEDs. The present work reports on the characterization of InGaN/GaN based LED structures by Atomic Force Microscope (AFM), which aimed at the detailed study of surface morphology and defect structures. The electrical properties of defects were studied by Electron Beam Induced Current (EBIC) and the luminescence properties of these LEDs were studied by Electroluminescence (EL).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
