To develop porous Si as substrate for better quality GaN layer
In this work, we prepare porous Si substrates via anodic etching process. The etching parameters such as time and current would be optimized for the best porous substrate, which is defined by having high porous density. The estimated average of porous density of the substrate is determined through the observation via scanning electron microscopy (SEM). After that, a thin GaN film is deposited onto the best porous Si substrate, using RF-sputtering machine. The grown layer is then will be characterized by photoluminescence (PL), X-ray diffraction (XRD) and Hall-effect measurements. As a comparison, we also grow and characterize a thin GaN on non-porous Si substrate, with the adoption of AlN buffer layer.
Growth of crack-free hexagonal GaN films on Si(100)
Hexagonal GaN films have been grown on Si(100) substrates by employing a sputtered AlN buffer layer followed by another high-temperature metalorganic chemical vapor deposition (MOCVD) grown AlN buffer layer. The highly oriented structure of sputtered AlN provides a hexagonal template for subsequent AlN and GaN growth. The GaN films are evaluated by transmission electron microscopy, selected area electron diffraction, x-ray diffraction, and photoluminescence and exhibit a purely hexagonal columnar structure. The orientation of the GaN columns depends on the thickness of both the sputtered AlN buffer layer and the MOCVD grown AlN buffer layer. The surface of GaN films is shiny and crack free up to a thickness of 2 μm studied in this work.
Multicolored light emitters on silicon substrates
We demonstrate the operation of multicolored light emitting diodes (LEDs) on a silicon wafer using ultraviolet/violet GaN LEDs grown by molecular beam epitaxy on Si(111) in conjunction with organic dye based color converters. These organic converters, applied on top of the nitride diodes, absorb the nitride LED electroluminescence at ∼360 nm, and fluoresce in the green (∼530 nm), and orange (∼600 nm). In this fashion, multicolored light emitters may be made to operate side by side and monolithically on the same Si wafer in an approach that may be attractive for miniature GaN based full color displays.