• AlGaN;
  • AlGaN-channel HEMT;
  • AlN;
  • HEMT;
  • HFET;
  • 2DEG


We have demonstrated a high sheet carrier concentration in AlGaN-channel high-electron-mobility transistors (HEMTs) with AlN barrier layer. We investigate the epitaxial structure of these HEMTs by X-ray diffraction and reveal that the partial lattice relaxation occurs in the Al0.51GaN-channel layers on the AlN buffer layers, and that the AlN barrier layer was coherently grown on the AlGaN channel layer. The sheet carrier concentration due to two-dimensional electron gases of the AlN/Al0.51GaN HEMT is 2.8 × 1013 cm−2, which is enhanced owing to the use of AlN as the barrier layer. This value of the sheet carrier concentration agrees with the calculated value based on the model of partial lattice relaxation in AlGaN channel layer.