Interplay of external and internal field effects on radiative recombination efficiency in InGaN quantum well diodes

Aizawa, Hiroaki; Soejima, K.; Hori, Atsuhiro; Satake, Akihiro; Fujiwara, K.

doi:10.1002/pssc.200564117

Cited by 8 publications

(9 citation statements)

References 14 publications

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“…We attribute this difference in the temperature-dependent EL variation pattern between high and low injection current levels for the green SQW-LED to the carrier capture efficiency, since the applied forward bias condition is very different. That is, under the high injection current with the higher forward bias the external forward field effects result in the enhancement of the carrier escape, being consistent with the PL results under the forward bias condition [11,12]. On the other hand, the carrier escape is significantly reduced under the decreased forward bias voltage for the low injection current even at low temperatures.…”

supporting

confidence: 85%

“…It is important to note that the higher field existing in the well decreases the radiative recombination rate due to the quantum confined Stark effect, which also causes the reduced EL intensity [13,14]. This observation is consistent with our recent PL results where the PL intensity decreases when the applied forward voltage exceeds +2 V [11,12] after reaching the maximum intensity around +2 V. Therefore, our results suggest importance of the efficient carrier capture processes for explaining the observed enhancement of radiative recombination in the presence of high-density misfit dislocations.…”

supporting

confidence: 85%

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Significance of vertical carrier capture for electroluminescence efficiency in InGaN multiple‐quantum well diodes

Inada

Satake

Fujiwara

2007

Phys. Status Solidi (c)

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The electroluminescence (EL) spectral intensity has been investigated in the high-brightness green InGaN multiple-quantum-well light emitting diode (LED) in comparison with the single-quantum-well LED over a wide temperature range and as a function of injection current. It is found that the EL variation pattern with temperature and current is dramatically improved when the number of active wells increases as a result of enhanced carrier capture. The importance of vertical carrier capture processes is pointed out to explain the anomalous EL intensity variations at low temperatures.1 Introduction Blue and green light emitting diodes (LEDs) using group III-nitride semiconductor quantum structures have been manufactured successfully [1][2][3][4]. Such quantum well LEDs with a ternary alloy active layer shows very bright emission characteristics in spite of the existence of high-density misfit dislocations. Thus, origins of the high quantum efficiency have been receiving much attention [5][6][7][8][9][10]. Recently we have investigated temperature dependence of the electroluminescence (EL) spectral intensity in the super-bright green and blue InGaN single-quantum-well (SQW) LEDs, which reveals anomalous EL quenching at lower temperatures below 100 K [6][7][8]. It is found that the anomalous temperature dependence of the EL efficiency is caused by interplay of the carrier capture and the internal quantum efficiency. In this paper, the EL spectral intensity is investigated in the high-brightness green InGaN multiple-quantum-well (MQW) LED over a wide temperature range and as a function of injection current level in comparison with the green single-quantum-well (SQW) LED. It is found that the variation pattern of the temperature-dependent EL efficiency dramatically changes when the number of wells increases to four from one, suggesting that the carrier capture plays a very important role for the determination of EL efficiency.

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confidence: 85%

supporting

confidence: 85%

Significance of vertical carrier capture for electroluminescence efficiency in InGaN multiple‐quantum well diodes

Inada

Satake

Fujiwara

2007

Phys. Status Solidi (c)

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“…Another issue is the observed blue shift of the emission with increasing drive current and the question whether it is related to the filling of Indium clusters/inhomgeneities or if it is due to the screening of the strong quantum well (QW) internal piezoelectric fields (PF) [3]. The estimation of the PF inside the InGaN QWs via reverse bias photoluminescence (PL) measurements and the investigation of the luminescence and photocurrent (PC) properties [4][5][6][7][8][9][10][11][12] as a function of bias and temperature has been a work horse of the analysis of InGaN LEDs since their advent in the late 90s and it is without question that a PF of significant strength exists inside the QW influencing the emission properties. However the interpretation of these experiments requires a detailed model that is able to realistically describe the alloy and doping profile of the LEDstructure and its influence on the potential profile and carrier densities inside the QW.…”

Section: Introductionmentioning

confidence: 99%

Self-consistent modeling of resonant PL in InGaN SQW LED-structure

Sabathil

Laubsch

Linder

2007

Light-Emitting Diodes: Research, Manufacturing, and Applications XI

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The measurement of the bias and temperature dependent photoluminescence, photocurrent and their decay times allows to deduce important physical properties such as barrier height, electron-hole overlap and the magnitude of the piezoelectric field in InGaN quantum wells. However the analysis of these experiments demands for a detailed physical model based on a realistic device structure which is able to predict the measured quantities. In this work a selfconsistent model is presented based on a realistic description of the alloy and doping profile of a green InGaN single quantum well light emitting diode. The model succeeds in the quantitative prediction of the quantum confined Stark shift and the associated change in the electron-hole overlap measured via the change in the bimolecular decay rate using literature parameters for the piezoelectric constants. The blue shift of the emission under forward current conditions can be attributed to the carrier induced screening of the piezoelectric charges as predicted by the model. The photocurrent is calculated via thermionic tunneling through the barriers using a WKB-approximation and the calculated potential profile for the tunneling barrier. From the fact that the bias and temperature dependence of the experimentally observed photocurrent cannot be described by the thermionic tunneling model even though the theoretical potential profile fits excellent to the luminescence data, we conclude that the carrier escape is dominated by a different mechanism such as defect-or phonon-assisted tunneling.

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“…Therefore, η ex variations are in fact very large for the blue diode and show dramatic dependence on the current level [24]. We attribute the strong η ex reduction at higher injection currents, observed for the blue MQW diode, to the carrier escape out of the wells due to increased forward bias voltages (external field effects) [29]. Schematic potential diagrams for the (In,Ga)N SQW diode with including the internal field opposite to the p-n junction field are shown in Fig.…”

Section: Units) T E M P E R a T U R E ( K ) W A V E L E N G T H ( N M )mentioning

confidence: 89%

Comparative study of electroluminescence efficiency of blue (In,Ga)N and red GaAs quantum-well diodes

2008

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Electroluminescence (EL) efficiency of a bright blue (In,Ga)N quantum-well (QW) diode has been studied in comparison with a high quality GaAs QW diode over a wide temperature range and as a function of current. For the red diode the EL intensity increases in directly proportional to the current at 20 K, indicating a nearly unity external quantum efficiency, although the EL efficiency is influenced by the transport of electrically injected carriers and nonradiative processes at higher temperatures. For the blue diode, however, the room temperature EL efficiency is surprisingly high, although the low-temperature EL efficiency is found to be quite low at high injection and significantly varied with current. These variations of the EL efficiency with current and temperature for the blue diode are attributed to the carrier capture and escape processes influenced under the internal piezo-field effects as a function of forward bias voltage.

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Interplay of external and internal field effects on radiative recombination efficiency in InGaN quantum well diodes

Cited by 8 publications

References 14 publications

Significance of vertical carrier capture for electroluminescence efficiency in InGaN multiple‐quantum well diodes

Significance of vertical carrier capture for electroluminescence efficiency in InGaN multiple‐quantum well diodes

Self-consistent modeling of resonant PL in InGaN SQW LED-structure

Comparative study of electroluminescence efficiency of blue (In,Ga)N and red GaAs quantum-well diodes

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