Showing papers by "Peter Hacke published in 2000"

Doping-dependent optical gain in GaN

Abstract: We report on an investigation of the optical gain in undoped and Si-doped metal-organic vapor phase epitaxially grown GaN. For carrier densities around the Mott transition (at approximately 8×1017 cm−3), the optical gain was observed to increase from around 102 cm−1 up to about 103 cm−1, suggesting a much larger optical gain for an electron-hole plasma than for excitons. A maximum optical gain of 2700 cm−1 at an excitation density of 9.2×1018 cm−3 was found for undoped GaN. This value is the highest achieved for epitaxially grown GaN, verifying the high potential for low-threshold lasing in this material. The optical gain was observed to decrease with increasing doping density. On the contrary, the luminescence efficiency was found to increase up to a doping density of approximately 1018 cm−2. Together these effects create an optimum doping density of around 5×1017 cm−2 for stimulated emission in bulk GaN.

Origin of the nonradiative 〈112̄0〉 line defect in lateral epitaxy-grown GaN on SiC substrates

Abstract: Nonradiative line defects are observed by cathodoluminescence in 〈2110〉 directions in [1100]-oriented GaN stripes grown by lateral epitaxy on SiC substrates Using transmission electron microscopy, the origin is determined to be principally screw dislocations We observe the screw dislocations in vertically [0001] stacked configurations and forming dislocation loops and half loops contained in two of the three planes of the form {1100} The dislocations are believed to serve to relax the anisotropic stresses experienced in the lateral epitaxy-overgrown stripes