Influence of growth temperature on GaN:Cr incorporation and structural properties in MOVPE

The influence of the growth temperature in metal organic vapor-phase epitaxy (MOVPE) on intentional Cr incorporation during GaN growth is studied in the range 900-1125 °C. The structural properties are investigated and compared to those obtained from undoped layers deposited at the same growth conditions and using the same growth procedure; Whereas, the best surface morphology and the best crystal quality are found at 1125 °C for undoped GaN layers, the best structural and morphological properties are obtained for the Cr-doped GaN (GaN:Cr) layers grown at 950 °C. GaN:Cr layers deposited at this temperature additionally exhibit the highest Cr concentration in the series as well as a Cr accumulation in the beginning stage of GaN:Cr growth. The accumulation may be responsible for the changed growth mode and the improved structural characteristics as well as for the observed V-shaped defects usually associated with strain relaxation. Thermo-remanent magnetization and a hysteresis loop were observed even above room temperature. The magnetic properties correlate to the structural properties of GaN:Cr layers.