Physical Properties of Bulk GaN Crystals Grown by HVPE

Abstract

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.

Dislocation Reduction in AlN and GaN Bulk Crystals Grown by HVPE

“…GaN and AlN epitaxial layers were grown up to 100 to 200 mm thickness by HVPE onto 6H-SiC(0001) and Si(111) substrates respectively (for details of the growth processes see [6]). The growth temperatures range from 1120 to 1320 K, the growth rate is about 0.06 mm/h.…”

High Pressure Luminescence of Zincblende and Wurtzite GaN

“…If one assumes a linear volume dependence of the energies, No experimental values of B 0 exist yet for cubic GaN. We have used B 0 200 GPa for both hexagonal and cubic GaN, which seems to be reasonable, because the bulk modulus depends mainly on the nearest-neighbor distance [14,15], which is almost the same in cubic [16,17] and hexagonal [17,18] GaN. In the fitting procedure the values for a (but not those for b) turn out to be almost independent of the parameter B 0 .…”

Epitaxial strain energy measurements of GaN on sapphire by Raman spectroscopy

“…Given potential run-to-run variations in the sample strain state, the latter approach is preferred. The Raman shift of the GaN E 2 mode has been reported by several groups, and the reported values vary in the relatively large range 565 to 572 cm -1 [2,3], reflecting differences in the residual strain in the epilayer after growth and thus the sensitivity of the method. The reported shifts of the E 2 mode for freestanding GaN samples, however, show the relatively wide range 566-568 cm -1 [2][3][4][5], suggesting that freestanding GaN films grown by HVPE techniques usually contain high impurity levels, resulting in hydrostatic stress.…”