MOVPE growth of N-polar GaN/AlxGa1−xN/GaN heterostructure on small off-cut substrate for flat interface

The smooth surface of an N-polar GaN/Al
x
Ga
1−x
N/GaN heterostructure was successfully grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates with a small off-cut angle of 0.8° toward the a-plane. The 2DEG of an N-polar GaN/Al
x
Ga
1−x
N/GaN heterostructure has been confirmed by Hall-effect measurement from 17 to 300 K. The sheet carrier concentration and the 2DEG mobility of this heterostructure were measured to be 1.4 × 10
¹³
cm
⁻²
and 1250 cm
²
/Vs at room temperature, respectively. The mobility monotonically increased with decreasing temperature and saturated at a value of 3050 cm
²
/Vs at 17 K. These values obtained in the primitive experimental show the potential of an N-polar GaN HEMT.