Fumiharu Teramae

Fabrication technique for moth-eye structure using low-energy electron-beam projection lithography for high-performance blue-light-emitting diode on SiC substrate

To realize high-efficiency light-emitting diodes (LEDs), it is indispensable to increase light extraction efficiency. We propose the moth-eye structure on the surface of an LED chip, which consists of periodic cones with a pitch of optical wavelength scale, and enables the significantly enhancement of light extraction efficiency. We have developed a new technique for moth-eye structure fabrication, on the basis of low-energy electron-beam projection lithography (LEEPL), which can be applied to the mass production of LEDs. The moth-eye structure formed at the bottom of a SiC wafer has periodically arranged cones with a 300 nm pitch and a 750 nm height. We also present blue LEDs fabricated on SiC substrates with and without the moth-eye structure, and discuss the effect of the moth-eye structure on the performance of LEDs.

Precise Control of Vertical-Cavity Surface-Emitting Laser Structural Growth Using Molecular Beam Epitaxy In Situ Reflectance Monitor

A vertical-cavity surface-emitting laser (VCSEL) was fabricated using a in situ reflectance monitor by molecular beam epitaxy (MBE). Both the center wavelength of the stop band of the distributed Bragg reflector (DBR) and the resonant wavelength of the optical cavity were successfully controlled using the monitor. However, these wavelengths shifted with decreasing substrate temperature after the growth, which could be reasonably explained by the temperature dependence of refractive index. Therefore, it is necessary to set a target wavelength at a growth temperature, considering the change. The desirable laser performance of the VCSEL fabricated from the wafer indicates marked increases in the controllability and reproducibility of growth with the aid of the in situ reflectance monitor. Since it can directly measure the optical properties of the grown layers, the reflectance monitor greatly helps in the fabrication of a structure with the designed optical performance.