Growth experiments with GaN in the system Ga/HCl/NHJHe at different growth temperatures show that the assumption of N-vacancies t o be responsible for the high n-conductivity is questionable. The dependence of carrier concentration on growth temperature as well as the decrease in carrier concentration when additionally purified NH, is used indicate that donor impurities are incorporated. The most probable impurity is oxygen, substitutionally incorporated onto N-sites. The observed growth rate dependence of carrier concentration can well be explained by a kinetically controlled incorporation process.Wachstumsexperimente mit GaN im System Ga/HCl/NH,/He bei verschiedenen Wachstumstemperaturen zeigen, daB die Annahme von N-Vakanzen als der Ursache der hohen n-Leitung in GaN fraglich ist. Die Abhangigkeit der Tragerkonzentration von der Wachstumstemperatur als auch der Abfall in der Tragerlronzentration bei Einsatz von zusatzlieh gereinigtem NH, weisen darauf hin, daR Donatorverunreinigungen eingebaut werden. Die wahrscheinlichste Verunreinigung ist Saucrstoff, substitutionell eingebaut auf N-Platzen. Die beobachtete Wachstumsratenabhangigkeit der Tragerkonzentration kann gut durch einen kinetisch kontrollierten EinbauprozeB erklart werden.

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In contrast to usual quantum wells or barriers having a thickness of some lattice constants, spatially well-separated, electronically uncoupled monolayers of group-III or V elements are considered as isovalent δ doping or δ layers. Similar to the case of randomly distributed nitrogen dopants in GaP bulk material, it is shown that the two-dimensional arrangement of isovalent atoms brings forth a new quality of III-V semiconductor compounds: The optical emission and absorption properties near the fundamental band gap of indirect-gap, and even of direct-gap, host material, where the isovalent layers are incorporated, are drastically improved. Low-temperature luminescence and transmission experiments on metal-organic vapor-phase epitaxially grown InAs δ layers in GaAs, AlAs δ layers in GaAs, and GaAs monolayers in AlAs are dealt with.

Interdiffusion coefficients on the group V sublattice of GaAs were determined in GaAsP/GaAs and GaAsSb/GaAs superlattices. Strained GaAs 0.86 P 0.14 /GaAs, GaAs 0.8 P 0.2 /GaAs 0.975 P 0.025 and GaAs 0.98 Sb 0.02 /GaAs superlattices were annealed between 850°C and 1100°C under different arsenic vapor pressures. The diffusion coefficient was measured by secondary ion mass spectroscopy and cathodoluminescence spectroscopy. The interdiffusion coefficient was higher under arsenic-rich conditions than under gallium-rich conditions, pointing to an interstitial-substitutional type of diffusion mechanism.