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Free standing GaN platelets were fabricated by hydride vapor phase epitaxy (HVPE). The platelets having a current maximum size of 7×6×0.1 mm3 were obtained by HVPE growth of ~100 μm thick GaN layers on SiC substrates and subsequent removal of the substrates by reactive ion etching (RIE). Surface of the GaN platelets was characterized by reflectance high energy election diffraction (RHEED), and Auger electron spectroscopy (AES). Crystal structure and optical properties of the platelets were studied by x-ray diffraction and photoluminescence (PL), respectively. Raman spectroscopy was also applied for material characterization. Residual strain was detected in the crystals. The stress was eliminated by high temperature anneal.

We report on nickel based technology for the fabrication of GaN mesa structures. Ti/Ni ohmic contacts for n-doped GaN with contact resistivity R c ~2×10 -5 Ω ×cm 2 and Ni ohmic contacts for p-doped GaN with R c ~ 4×10 -2 Ω ×cm 2 were formed. Both types of contacts were used as masks for GaN reactive ion etching (RIE) in a CCl 2 F 2 /Ar gas mixture. Maximum etch rates of ~ 40 nm/min were obtained. Mesa structures up to 3 µm in height were formed.

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