Abstract
We optimized the growth conditions of AlGaN layers using a large-size horizontal metalorganic vapor-phase epitaxy (MOVPE) system, and different-Al-content Al
x
Ga
1−
x
N/GaN heterostructures (0.26 ⩽
x ⩽ 0.70) were successfully grown on 100-mm-diameter sapphire substrates. It was confirmed that a good in-wafer uniformity of the alloy composition, within ±3%, was obtained even for the sample with the highest Al content of 0.70 and that no relaxation in the AlGaN layers occurred for all samples. A minimum sheet resistance of approximately 380
Ω/sq (sheet carrier concentration=1.76×10
13/cm
2) with good in-wafer uniformity was obtained for the sample with the Al content of 0.52.