UOMI Kazuhisa Hitachi, Ltd., Central Research Laboratory, Senior Reseacher, 中央研究所, 主任研究員
KADOYA Yutaka Hiroshima University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (90263730)
|Budget Amount *help
¥12,700,000 (Direct Cost : ¥12,700,000)
Fiscal Year 1999 : ¥5,800,000 (Direct Cost : ¥5,800,000)
Fiscal Year 1998 : ¥6,900,000 (Direct Cost : ¥6,900,000)
In this project, we studied the spontaneous-light emitting devices, which exhibit the directional radiation with high efficiency and has a capability of very high speed switching, using semiconductor microcavities. Particularly, aiming at the practical application, we focused on the realization of such devices working at room temperature.
In the first year (1988), we studied the operation at low temperature in detail in the microcavity light-emitting triode which had been already fabricated. The device has both the functions of current injection and the application of static electric field to the quantum well. Under the constant current injection, we confirmed the continuous change of emission wavelength with the change of the voltage applied to the quantum well, and the change of emission intensity associated with the wavelength-change. The intensity was peaked when the emission wavelength is tuned to the cavity resonance. In addition, the radiation patterns were varied with the change
of the emission wavelength. From these results, we concluded that the spontaneous emissions were altered by the presence of the microcavity under the control of emission wavelength by the voltage applied to the device. However, the radiation pattern in the device was asymmetric. Through the experiment, we speculated that the reason of the asymmetric radiation is related the local carrier injection due to the difference of resistance between the conducting layers thorough which the p-n junction is biased.
In the second year (1999), we re-designed the device. We characterized the new devices at room temperature, and found that the radiation patterns were symmetric. In addition, we confirmed the basic functions of the device, namely the change of radiation pattern and intensity with the change of emission wavelength by the change of the bias voltage applied to the devices, under the injection of carriers by current. Hence, we can conclude that the spontaneous light emitters based on semiconductor microcavities were confirmed to work well at room temperature. Unfortunately, however, the external quantum efficiency was very low, most likely to be due to the poor crystalline quality. Therefore, to apply the devices in practical use, it is necessary to realize higher quality materials in future. Less