Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells

Abstract

Electroluminescence spectra of light-emitting diodes based on InGaN/AlGaN/GaN heterostructures with single and multiple quantum wells (QWs) are analyzed by models of radiative recombination in 2D-structures with band tails. Equations of the model fit spectra quite good in a wide range of currents. Parameters of the fit are discussed and compared for single and multiple QWs. Tunnel effects play a sufficient role in blue LEDs with single QWs at low currents; they can be neglected in LEDs with multiple QWs. A new spectral band was detected at the high energy side of the spectra of green LEDs with multiple QWs; it is attributed with large scale inhomogenities of In distribution in InGaN QWs.)

Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells

“…3 (see a method of measurements in [8]). The LEDs with MQWs have wider space charge width than ones with SQWs [2][3][4][5]7]; in both cases the width for green LEDs is wider than for blue ones. This fact corresponds to a low probability of tunnel effects in the LEDs with MQWs.…”

“…The maximum of this band is moving with the current J and voltage on the active layer U: hω max = eU+∆ (in the range = 2.1-2.3 eV). This band was described as a tunnel radiative recombination [4,5]. There is no tunnel band in blue LEDs with MQWs; in this case the blue line is moving with V.…”

“…Low currents could be understood as a tunnel component; tunnel currents in these LEDs play some role at J 3-4 orders of magnitude lower than that for SQWbased LEDs [2][3][4][5]7]; J(V) curves of SQW-based LEDs differed from MQW-based LEDs because of a wider active layer [1]. A good approximation of the J(V) curves for MQW LEDs was done when not only a series resistance R s at the linear part at higher J was taken into account, but also the quadratic part: J ( V-V 1 )…”

“…We have studied luminescence spectra of two groups of LED's based on structures with single InGaN quantum wells (SQWs, sent to Moscow University by Dr. S.Nakamura, Nichia Chemical Co.) and multiple quantum wells (MQWs, sent to Moscow University by Dr. M.Koike, Toyoda Gosei Co.) in a wide range of currents [2][3][4][5][6]. A model of radiative recombination in 2D-structures with band tails caused by potential fluctuations was successfully applied to describe the spectra [2][3][4]; tunnel radiative recombination was detected at low currents [5]. In this work spectra of blue and green LEDs with SQW and MQW active layers are compared and the model of recombination is analyzed.…”

Changes in electrical characteristics associated with degradation of InGaN blue light-emitting diodes

“…Recently, the threading dislocations have been identified as non-radiative recombination centers by a study of plan-view transmission electron microscopy along with cathodoluminescence (CL) 2 and found to be a major origin for the high reverse-bias leakage currents in p-n diodes by comparing diodes fabricated on dislocated GaN and LEO (lateral epitaxial overgrowth) GaN. 3 In fact, the study of reverse-bias leakage currents in GaN p-n photodiodes, 4 in InGaN blue LEDs, [5][6][7] and even in metalsemiconductor-metal ultraviolet photodetectors 8 has become an important subject, since it is an effective method for the investigation of defect-related conduction under high electric fields. All these studies have indicated that the reverse-bias leakage current is related to carrier tunneling or hopping through the defect states within the bandgap in the GaN-based materials.…”