Nanojunction Light Emitting Devices

In 1994, Katsuyama et al. [180] fabricated GaAs p-n nanowhisker junction based on reduced-pressure metal-organic vapor-phase epitaxy. Intense light emission was observed during carrier injection to the p-n junction formed in the GaAs whisker. The emitted light showed strong polarization anisotropy, which was explained by the quantum confinement effect. Recently, Gudiksen et al. [14] reported a method to synthesize p-n junctions. In order to create a single junction within a nanowire, the addition of the first reac-tant is stopped during growth, and then a second reactant is introduced for the remainder of the synthesis. Nanojunction with different elements or different major carrier types was obtained.

Using this method, InP nanowire p-n junction was fabricated. Besides this nanojunction showing rectifier behavior, light emitted from the p-n junction was observed as shown in Figure 21. The polarization direction is found to be along that of the nanowire. The light emission was found blue-shifted due to the one-dimensional structure and radial quantum confinement. The efficiency of their intra-nanowire LEDs is around 0.1%, which can be improved by optimizing the devices. Recently, electrically driven las-ing from single n-type CdS nanowire was achieved by Duan and his colleagues [181]. More exciting demonstrations on application of nanowire junctions can be expected and are appearing.

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