Blue to yellow emission from (Ga,In)/GaN quantum wells grown on pixelated silicon substrate

It is shown that substrate pixelisation before epitaxial growth can significantly impact the emission color of semiconductor heterostructures. The wavelength emission from InxGa1-xN/GaN quantum wells can be shifted from blue to yellow simply by reducing the mesa size from 90 × 90 µm2 to 10 × 10 µm2 of the patterned silicon used as the substrate. This color shift is mainly attributed to an increase of the quantum well thickness when the mesa size decreases. The color is also affected, in a lesser extent, by the trench width between the mesas. Cathodoluminescence hyperspectral imaging is used to map the wavelength emission of the InxGa1-xN/GaN quantum wells. Whatever the mesa size is, the wavelength emission is red-shifted at the mesa edges due to a larger quantum well thickness and In composition.

Light Power Enhancement of Violet LEDs Using AlGaN-Based Epitaxial Structure

The growths of AlN and AlGaN materials were carried out in a home-built metal organic chemical vapor deposition (MOCVD) system. The AlN template was characterized by X-ray diffraction (XRD) and it showed the full width at half magnitude (FWHM) of the x-ray (002) scan rocking curve was only 28 arc seconds, while the FWHM of (102) plane was 252 arc seconds. The results suggested a high quality epitaxial material was obtained. Subsequently, an AlGaN-based violet LED was designed on this template by using AlGaN material as the base. The Al composition of electronic blocking layer (EBL) was optimized. By a quick on-wafer electroluminescence (EL) test, it was demonstrated that the output light intensity of the new structure was at least 15% stronger in comparison to that of the traditional GaN-based violet LED. Finally, fully packaged LEDs were fabricated and the luminous power of the new structure was measured by Spherical integrated system. It was confirmed that a 43% increase of the output power can be obtained.