Effect of QW growth temperature on the optical properties of blue and green InGaN/GaN QW structures

Abstract

In this paper we report on the impact that the quantum well growth temperature has on the internal quantum efficiency and carrier recombination dynamics of two sets of InGaN/GaN multiple quantum well samples, designed to emit at 460 and 530 nm, in which the indium content of the quantum wells within each sample set was maintained. Measurements of the internal quantum efficiency of each sample set showed a systematic variation, with quantum wells grown at a higher temperature exhibiting higher internal quantum efficiency and this variation was preserved at all excitation power densities. By investigating the carrier dynamics at both 10 K and 300 K we were able to attribute this change in internal quantum efficiency to a decrease in the non‐radiative recombination rate as the QW growth temperature was increased which we attribute to a decrease in incorporation of the point defects. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Disentangling the Impact of Point Defect Density and Carrier Localization-Enhanced Auger Recombination on Efficiency Droop in (In,Ga)N/GaN Quantum Wells

“…Nevertheless, the relative emission efficiency of the samples is consistent with expectations, i.e., at all of the N 0 ’s studied, it increases with T G , consistent with the lower incorporation of point defects at higher growth temperatures. The relative performance of the three samples shown in Figure a is also consistent with the IQE values reported previously in the literature at lower excitation rates. However, what is most notable is the remarkable similarity of the behavior of the three samples at high N 0 values (>1 × 10 19 cm –3 ), which is most readily evident when comparing normalized versions of the droop curves, as shown in Figure b.…”

“…This relative emission efficiency can be used as a proxy for IQE even though, as shown below, it is proportional to the IQE time-averaged over the decay of the carrier density. Each of the samples, described in detail in the Methods section, is labeled by its QW growth temperature, T G , in °C, which has previously been shown for these samples to inversely correlate with increased SRH recombination and so is consistent with a positive correlation with point defect density . Our previous studies also revealed that the emission efficiency measured in this way under identical experimental conditions can exhibit significant point-to-point variation across the sample, in a similar way to other reports that attributed it to the effect of step edges on local point defect density .…”

“…This may be achieved by utilizing QWs grown along alternate crystal directions or in alternate phases that have lower recombination lifetimes, τ, since N = j τ/ et QW , where t QW is the QW thickness. For instance, QWs produced from m -plane wurtzite or zincblende GaN have sub-nanosecond recombination lifetimes rather than lifetimes of 10s or 100s of nanoseconds as typically found for c -plane wurtzite green-emitting QWs . However, no significant reduction in droop has yet been observed in nonpolar QWs , and droop measurements in zincblende GaN QWs have yet to be reported.…”

“…15,16 In this way, we investigate the effect of point defect density on droop by comparing measurements performed on a series of green-emitting cplane (In,Ga)N/GaN QWs designed to have the same density of extended defects but different point defect densities, controlled by varying the growth temperature of the (In,Ga) N QW. 17 The experimental studies are accompanied by theoretical studies that provide insight into the N-dependence of the carrier localization-enhanced radiative and Auger recombination rates. The atomistic tight-binding model accounts for (i) a microscopic description of the alloy disorder, (ii) the resulting fluctuations in strain and polarization fields, (iii) realistic length scales relevant to carrier localization effects, and (iv) the screening of the polarization field as carrier density increases in the (In,Ga)N/GaN QWs.…”

Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes

“…First, the indium incorporation is sensitive to the growth conditions, such as growth temperature, growth rate, V/III ratio 6 , and the hydrogen flow rate 7 . In addition, the growth temperature of InGaN should be much lower than GaN due to the low dissociation temperature of InN 8 . In fact, the growth of InGaN epilayer has to be performed at temperature range of 650–850 °C.…”