We used high-pressure grown GaN single crystal substrates to fabricate dislocation free optoelectronic devices like light emitting diodes and laser diodes structures. The latter ones demonstrated laser action under optical pumping condition with the threshold of about 200 kW/cm2 at room temperature. In the present paper we would focus on the specific aspects of the homoepitaxial growth by MOVPE method including epi-ready substrate preparation and surface polarity choice. We believe that our results demonstrate clearly the feasibility of device fabrication based on high-pressure grown GaN bulk crystals.

Structural properties of GaN/GaAlN multiple quantum wells (MQW) grown by nitrogen plasma assisted MBE on MOCVD-grown GaN/sapphire (GaN pseudosubstrates) have been characterised by X-ray reciprocal lattice mapping to determine the strain and composition of ternary alloys. The results clearly demonstrate that the barriers of GaAlN with up to 17% of aluminium content grown by plasma assisted MBE on GaN are fully strained. Optical properties have been characterised by low temperature photoluminescence. Photoluminescence emission peaks corresponding to the GaN/GaAlN MQW structures revealed strong red-shift with respect to the GaN energy gap. This can be explained by a strong internal electric field present in the QW's which is attributed to a transfer of piezoelectric field due to Fermi-level alignment.