Fig. 1. (a) Schematic structure of AlGaN MQWs with IDBs AFM images of (b) III-polar and (c) N-polar AlGaN MQWs in a 20  μm×20  μm region. Top view SEM images of MQWs near IDBs (d) before and (e) after KOH etching.

Fig. 2. Steady-state (a) PL spectra and (b) PL decay curves of single-polarity MQWs and MQWs with IDBs.

Fig. 3. Schematics of atomic arrangements and corresponding electronic potential distributions near IDBs for (a), (b) GaN; (c), (d) Al0.5Ga0.5N; and (e), (f) AlN.

Fig. 4. Electronic potential of the free surface of (a) GaN and (b) AlN comprising both [0001] and [000–1] directions.

Fig. 5. (a) Surface potential distribution and (b) corresponding topography image of AlGaN MQWs with IDBs in the center. (c) Line-scan of the potential as indicated by the red line in the KFM mapping.

Fig. 6. VB spectra and cutoff values measured from N- and III-polar AlGaN MQWs via UPS.

Fig. 7. Lateral band diagram of AlGaN MQWs with IDBs located in the center.

Fig. 8. DOS calculation of AlN with IDBs in the center. The left side indicates III polarity, and the right side indicates N polarity.