First AlGaN Free-Standing Wafers

Abstract

AbstractSingle crystal AlGaN bulk materials have been fabricated, for the first time. AlGaN thick (up to 0.6 mm) layers were grown by hydride vapor phase epitaxy on SiC substrates. The substrates were removed resulting in free-standing AlGaN wafers up to 0.5 inch in diameter. Fabricated AlGaN wafers were investigated by x-ray diffraction, transmission electron microscopy (TEM), and cathodoluminescence. X-ray diffraction and TEM studies confirmed single crystal structure of grown material. Based on x-ray diffraction results, AlN concentration in grown material was estimated of about 35 mol.%. Cathodoluminescence measurements demonstrated a number of peaks in UV spectral region with the most intense luminescence at a wavelength of about 325 nm (100 K). The wafers demonstrated n-type conductivity with electron concentration in the 1017 cm-3 range at room temperature. Development of AlGaN substrates with controlled alloy composition may lead to stress-free device epitaxial structures for AlGaN-based transistors and UV emitters and sensors.