Continuous Alloy-Composition Spatial Grading and Superbroad Wavelength-Tunable Nanowire Lasers on a Single Chip

Department of Electrical Engineering, Arizona Institute of NanoElectronics, Arizona State University, Tempe, Arizona 85287, USA.
Nano Letters (Impact Factor: 13.59). 02/2009; 9(2):784-8. DOI: 10.1021/nl803456k
Source: PubMed


By controlling local substrate temperature in a chemical vapor deposition system, we have successfully achieved spatial composition grading covering the complete composition range of ternary alloy CdSSe nanowires on a single substrate of 1.2 cm in length. Spatial photoluminescence scan along the substrate length shows peak wavelength changes continuously from approximately 500 to approximately 700 nm. Furthermore, we show that under strong optical pumping, every spot along the substrate length displays lasing behavior. Thus our nanowire chip provides a spatially continuously tunable laser with a superbroad wavelength tuning range, unmatched by any other available semiconductor-based technology.

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Available from: Cun-Zheng Ning
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    • "Ternary alloy semiconductors, such as CdS x Se 1−x , are particularly intriguing for both scientific studies and technological applications . As the bandgap of CdS x Se 1−x can span the entire visible spectrum through alloy variation, it has potential applications as a light harvester in solar cells and a tunable wavelength source in semiconductor nanolasers [1] [2] [3]. The high defect density inherent to ternary alloys in comparison to their binary counterparts has led to reports of increased density of nonradiative recombination centres (Shockley- Read-Hall states) in AlGaAs [4] while exciton localisation in CdSSe nanobelts has been attributed to bandgap variation along the nanobelt [5]. "
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    ABSTRACT: We measure ultrafast carrier dynamics in a single CdSSe nanowire at different excitation fluences using an ultrafast Kerr-gated microscope. The time-resolved emission exhibits a dependence on excitation fluence, with the onset of the emission varying on the picosecond time scale with increasing laser power. By fitting the emission to a model for amplified spontaneous emission (ASE), we are able to extract the nonradiative carrier recombination lifetime and nongeminate recombination constant. The extracted nongeminate recombination constant suggests that our measurement technique allows the access to the nondiffusion limited recombination regime in nanowires with low carrier mobility.
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    • "These nanobelts have attracted great attention due to their widely-modulated band gap from 1.73 eV to 2.44 eV and their corresponding tunable optical properties [38]. Based on these, CdS x Se 1–x nanobelts have been constructed as the main component of nanoscale lasers [39] [40], waveguides [41] and field-effect transistors [38]. Despite the fact that most of the applications are based on the photoelectrical response of the CdS x Se 1–x nanobelts, to the best of our knowledge, a systematic and clear understanding of the photoconductivity in these nanobelts is absent so far. "
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    ABSTRACT: We employ optical pump-terahertz probe spectroscopy to investigate the composition-dependent photoconductivity in ternary CdSx Se1−x nanobelts. The observed carrier dynamics of CdS nanobelts display much shorter lifetime than those of ternary CdSx Se1−x nanobelts. This indicates the implementation of CdS nanobelts as ultrafast switching devices with a switching speed potentially up to 46.7 GHz. Surprisingly, ternary CdSx Se1−x nanobelts are found to exhibit much higher photoconductivity than binary CdS and CdSe. This is attributed to the higher photocarrier densities in ternary compounds. In addition, the presence of Se in samples resulted in prominent CdSe-like transverse optical (TO) phonon modes due to electron-phonon interactions. The strength of this mode shows a large drop upon photoexcitation but recovers gradually with time. These results demonstrated that growth of ternary nanostructures can be utilized to alleviate the high surface defect density in nanostructures and improve their photoconductivity.
    Full-text · Article · Aug 2013 · Nano Research
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    • "This property has been utilized in the past to grow materials with very different or graded alloy compositions [18] [19] [20] [21] to achieve light emission in a wide range, mostly from different wires and more recently from a single wire [25]. While we recently have demonstrated multicolor lasing from many wires on a single substrate [18], but so far, multi-color lasing from a single nanowire or belt has not been demonstrated, especially when the wavelength separation is wider than the gain bandwidth. "
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    ABSTRACT: The ability of a single monolithic semiconductor structure to emit or lase in a broad spectrum range is of great importance for many applications such as solid-state lighting and multi-spectrum detection. But spectral range of a laser or light-emitting diode made of a given semiconductor is typically limited by its emission or gain bandwidth. Due to lattice mismatch, it is typically difficult to grow thin film or bulk materials with very different bandgaps in a monolithic fashion. But nanomaterials such as nanowires, nanobelts, nanosheets provide a unique opportunity. Here we report our experimental results demonstrating simultaneous lasing in two visible colors at 526 and 623 nm from a single CdSSe heterostructure nanosheet at room temperature. The 97 nm wavelength separation of the two colors is significantly larger than the gain bandwidth of a typical single II–VI semiconductor material. Such lasing and light emission in a wide spectrum range from a single monolithic structure will have important applications mentioned above.
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