Electroluminescence properties of InGaN/GaN multiple quantum well-based LEDs with different indium contents and different well widths

Abstract

Two InGaN/GaN multiple quantum well (MQW)-based blue light emitting diodes (LEDs) emitting photons at approximately the same wavelength, with different indium contents and well widths, are prepared, and the temperature-dependences of their electroluminescence (EL) spectra at different fixed injection currents are investigated. The results show that, compared with sample B with its lower indium content and larger well width, sample A with its higher indium content and smaller well width, has a stronger carrier localization effect and higher external quantum efficiency (EQE) at the lower fixed currents; however, upon increasing the injection current, both the localization effect and EQE for sample A decrease at a faster rate. The former is mainly attributed to the deeper potential levels due to the larger indium fluctuations originating from the higher indium content, and to the smaller well width-induced stronger carrier quantum-confine effect (QCE); the latter is mainly attributed to the more significant growing in the electron leakage and/or electron overflow originating from the smaller well width and larger lattice mismatch-induced stronger piezoelectric field, and to the more significant reduction in carrier localization effect originating from the smaller well width-induced smaller density of high-energy localized states.

Wave-shaped temperature dependence characteristics of the electroluminescence peak energy in a green InGaN-based LED grown on silicon substrate

“…inside these three zones) at the highest current of 350 mA. Therefore, at 350 mA, the temperature behavior of peak energy is dominated first by thermalization of localized carriers inside these three zones from 6 to 220 K. Then, the dominated temperature behavior is shown as the regular thermalization of free carriers in the MQWs for the highest full-delocalization temperature range of 220-350 K 14,15,25 .…”

“…These behaviors can be explained by the fact that the relaxation process of the localized carriers related to the temperature inside the respective zones is gradually suppressed with increase of the fixed current from 0.001 to 0.5 mA. This may be due to the gradual reduction of the carrier localization effect inside their respective zones 14,15 . In contrast, the relaxation process of the localized carriers dependent on temperature from the shallower downwards to the deeper localized zone structure is still in progress due to the larger difference in the potential minima between these three zones, originating from their larger difference in the average In content.…”

“…This is because the former exhibits only a single S-shaped (redshift-blueshift-redshift) temperature dependence of the peak energy (i.e. one-step blueshift), and the one-step blueshift is attributed to the thermal broadening effect of the localized carriers in the MQWs including only one zone 10,14,15 ; the latter exhibits only a double S-shaped (redshift-blueshift-redshift-blueshift-redshift) temperature dependence of the peak energy (i.e. two-step blueshift), and the two-step blueshift is attributed to the thermal broadening effect of the localized carriers in the two zones with different potential barriers 24 .…”

“…Many different optical characteristics including the increasing temperature-induced thermal expansion and relaxation of localized carriers 9,10 , the band-filling for localization states of injected carriers 11,12 , and the enhancement of carrier transfer from shallow to deep localization states induced by carrier-scattering effect 13 , can be elucidated. Moreover, an inverted V-shaped temperature-dependent characteristic of the emission peak energy in a wide fixed injection current range is attributed to the higher homogeneity at the depths of these localized states 14 . Despite these, the carrier dynamics of the anomalous behaviors induced by temperature, especially for the EL in the InGaN/GaN MQWs-based LEDs with high In-contents, remain to be fully determined.…”

Влияние буферного слоя por-Si на структуру и морфологию эпитаксиальных гетероструктур In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N/Si(111)

“…Твердые растворы In x Ga 1−x N являются идеальными кандидатами для разнообразных оптоэлектронных применений. Благодаря тому, что ширина запрещенной зоны In x Ga 1−x N может изменяться в диапазоне энергий от 0.7 до 3.4 эВ, т. е. в зависимости от содержания индия может располагаться как в ИФ, так и в УФ диапазоне, эти твердые растворы активно используются как при конструировании свето-и лазерных диодов, так и солнечных элементов [1,2] Хорошо известно, что основной подложкой для эпитаксиального роста A III N соединений с гексагональной кристаллической решеткой является сапфир c-Al 2 O 3 . Однако использование монокристаллического кремния (c-Si) в роли подложки и его комбинация с A III N также весьма часто используется и имеет ряд преимуществ для промышленности, обусловленных уже тем фактом, что кремний -это основной материал современной электроники.…”