Time Resolved Optical Studies of InGaN Layers Grown on LGO

Cheung, M.; Namkoong, Gon; Furis, Madalina; Chen, Fei; Cartwright, Alexander N.; Doolittle, W. Alan; Brown, April S.

doi:10.1557/proc-743-l11.6

Cited by 1 publication

(1 citation statement)

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“…Specifically, stretched exponential decay and power law decay are associated with two well-known carrier dynamics models that are used to describe complicated decay mechanisms. For example, a stretched exponential function has been very successfully in fitting PL decay of porous silicon and InGaN [25][26][27][28][29], and is define by…”

Section: Theorymentioning

confidence: 99%

Ultrafast Carrier Dynamics and Recombination in Green Emitting InGaN MQW LED

et al. 2006

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Ultrafast spectroscopy, in particular time-resolved photoluminescence, can help in the development of InGaN/GaN heterostructures for long wavelength visible emitters. In this paper, we present recent results that underscore the current understanding of two approches to achieve desired emission characteristics and recombination mechanisms in InGaN/GaN MQWs for green LEDs. Specifically, the photoluminescence decay of samples grown using two different design approaches is discussed. In one approach, samples, with high indium incorporation, were grown on a high quality AlN substrate to achieve green emission. The resulting photoluminescence decay of the green luminescence is long-lived and non-exponential. Quantitative analysis showed that the decay is non-exponential and consists of a stretched-exponential decay component, at short times, followed by a power law decay component at longer times. This non-exponential decay, resulting in significant elongation of the radiative lifetime, is indicative of inhomogeneity in the quantum wells. Thus carrier localization, in a structure with low defect density, proves to be an effective means to achieve green emission. In another approach, a piezoelectric Stark-like ladder effect is used. In this case, a methodical layer-by-layer growth homogeneity optimization process was adopted to achieve an optical transition below the electron to heavy-hole (e 1 hh 1 ) transition when the quantum well is subjected to the presence of the strong piezoelectric polarization dipole. An advantage of this approach is that it has proven successful in achieving green luminescence on conventional sapphire substrates. The resulting photoluminescence decay at 14 K of a sample grown by this approach is single exponential and shorter in duration than the decay observed in the first approach. This exponential decay further supports previous AFM studies that revealed a homogeneous active region.

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