Influence of Defects on Current Transport in GaN/InGaN Multiple Quantum Well Light-Emitting Diodes
- PDF / 134,325 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 29 Downloads / 246 Views
Influence of Defects on Current Transport in GaN/InGaN Multiple Quantum Well LightEmitting Diodes X. A. Cao, E. B. Stokes, S. F. LeBoeuf, P. M. Sandvik, J. Kretchmer, and D. Walker Semiconductor Technology Laboratory, GE Research Center, One Research Circle, Niskayuna, NY 12309
ABSTRACT We have studied the electrical and optical characteristics GaN/InGaN based light-emitting diodes (LEDs) grown on sapphire using metalorganic chemical vapor deposition (MOCVD). Strong correlation has been found between material quality and the mechanism of current transport through the wide-bandgap p-n junction. Tunneling behavior dominates throughout all injection regimes in the devices with high-density defects in the space-charge region, which act as deep-level carrier traps. The approximately current-squared dependence of light output at low currents indicates dominant nonradiative recombination in the active region. However, in a high quality LED diode, tunneling current is only a major contributor at low forward biases. At moderate biases, temperature dependent diffusion-recombination current has been identified as I0 exp(qV/1.6kT). In these devices, nonradiative recombination centers are saturated at current densities as low as 1.4x10-2 A/cm2.
INTRODUCTION High brightness blue and green light-emitting diodes (LEDs) with the operation lifetime exceeding 104 hour has been demonstrated and commercialized based on III-V nitride alloys despite the presence of a large number of structural and electronic defects in these materials [1]. To further improve LED efficiency and reliability, it is essential to understand the effects of these defects on the carrier injection mechanisms and recombination processes in these devices. Several groups have reported that carrier tunneling rather than thermal diffusion and recombination dominates in InGaN/GaN-based double heterostructure (DH) LEDs due to a great number of defects present at the hetero-interfaces[2-4]. Unrealistic ideality factors of 4 - 6 in these devices were observed. Recently, Chitinis et. al.[5] demonstrated a high quality AlInGaN/InGaN multiple quantum well (MQW) light emitting diode structure by incorporation of a small amount of In into the AlGaN barrier layers. The electrical characteristics showed an ideality factor of 2.28, which is close to the theoretical prediction for carrier recombination in the space charge region. In this work, we present a study of electrical and optical properties of commercially available GaN/InGaN MQW blue LEDs. The similar epitaxial structure and dopant profile but different material quality in the LEDs enabled us to investigate the effects of microstructural defects on current transport across the p-n junctions. The correlation between electrical characteristics and optical performance was found based on results from currentvoltage (I-V) and electroluminescence (EL) measurements.
K2.3.1 Downloaded from https:/www.cambridge.org/core. University of Arizona, on 30 Apr 2017 at 08:10:54, subject to the Cambridge Core terms of use, available at h
Data Loading...
