Highly resistive GaN substrates for high frequency electronics

Bulk GaN crystals are regarded as the most promising candidates for substrates for optoelectronic, high power and high frequency electronic devices. In this paper some principles of ammonothermal method of bulk gallium nitride growth are presented. Excellent structural properties and wide spectrum of electrical parameters of obtained this way truly bulk GaN crystals are shown. In considered crystals a low dislocation density (5×10³ cm^-2) is attainable. High crystallinity is manifested by extremely flat crystal lattice and very narrow (FWHM=16 arcsec) X-ray rocking curves measured for (0002) plane. Ammonothermal GaN substrates enabled to grow high quality, strain-free homoepitaxial layers and AlGaN/GaN heterostructures. This may enable a breakthrough in manufacturing of aforementioned high power electronic devices.