| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM1-ThM |
| Session: | Materials for Light Management |
| Presenter: | Yue Kuo, Texas A&M University |
| Authors: | C.-C. Lin, Texas A&M University Y. Kuo, Texas A&M University X. Zhang, Xi’an Jiaotong University, China |
| Correspondent: | Click to Email |
LEDs has the low energy consumption, compact size, and long-lifetime [1]. Since the white light cannot be emitted from a single LED, a combination of red, green, and blue LEDs or an UV or blue LED with a yellow phosphor has to be used. Kuo and Lin proposed a new type of single-chip, white-light emission LED that is made of the amorphous high-k dielectric thin film on a Si wafer [2-5]. The light emission is from the thermal excitation of nano-size conductive paths formed during the dielectric breakdown, which is similar to the principle of the incandescent device. Its energy efficiency is expected to be much higher than that of the incandescent light bulb because of the small size conductive path. The emission light intensity and wavelength range of the LED were enhanced with the embedding of a nanocrystal layer in the high-k film paths [2]. Authors investigated optical and electrical characteristics of the ZrHfO/AlOx/ZrHfO LED.
The following results were obtained from this study. First, the AlOx embedded ZrHfO LED emits the broad band light including the visible to near IR wavelengths. Second, the emitted light falls into the warm white light region of the CIE 1931 color chart with a high color rendering index (CRI) of ~98. Third, the LED has a larger leakage current than the control sample, i.e., ZrHfO without the embedded AlOx layer, which is due to the stress mismatch between these two materials film [6]. Fourth, both the emission light intensity and the number of the bright dots increase with the inclusion of the AlOx layer and the increase of the magnitude of the stress voltage (|Vg|). These phenomena can be explained by the mechanism of thermal excitation of the conductive path. The large current density causes the high thermal excitation efficiency of the conductive path for the high intensity light emission. The larger number of conductive paths also contribute to the high emission intensity. Fifth, light emission was studied with the pulsed Vg driving method, i.e., at 1 kHz and -40 V, at various duty cycles (DCs). The spectrum wavelength range was independent of the change of DC. However, the peak height decreases with the decrease of the DC. It can be explained by the fast thermal excitation process of the extremely short conductive path, i.e., ~8.7 nm. The new LED can be an important white light source for many industrial, medical, etc. applications.
[1] N. Kimura, APL 90 051109 (2007)
[2] Y. Kuo et al., APL 102, 031117 (2013).
[3] Y. Kuo et al., Electrochem. Solid-State Lett. 2, Q59 (2013).
[4] Y. Kuo et al., Solid-State Electron. 89, 120 (2013).
[5] C. -C. Lin et al, JVSTB 32, 011208 (2014).
[6] C. -C. Lin et al, JVSTB 32, 03D116 (2014).