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Deep levels studies on a set of n-GaN films grown by MOCVD and HVPE reveal the presence of electron traps with levels near E c -0.25 eV, E c -0.55 eV, E c -0.8 eV, E c -1 eV, hole traps with levels near E v +0.9 eV and a band of relatively shallow states in the lower half of the bandgap. The total density of these latter states was estimated to be some 10 16 cm -3 and they were tentatively associated with dislocations in GaN based on their high concentration and band-like character. None of the electron or hole traps could be unambiguously related with strong changes of diffusion lengths of minority carriers in various samples. It is proposed that such changes occur due to different surface recombination velocities. An important role of E c -0.55 eV traps in persistent photoconductivity phenomena in n-GaN has been demonstrated.

Heteroepitaxial GaN and GaAs films were grown by both conventional two-step MOCVD and the new “capillary epitaxy” technique on (001) and (111) fianite (YSZ) substrates. The capillary epitaxy technique was investigated for the example of GaAs films growth on a YSZ substrate. This technique allows both the reduction of the minimum thickness and the improvement of the quality of III-V films. PL spectra of undoped GaN films on YSZ were studied.

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