Deep levels in KOH etched and MOCVD regrown GaN p‐n junctions

Abstract

Threading dislocations continue to challenge the functionality and reliability of GaN based devices. This work investigates the selective etching of threading dislocations in a GaN template grown by metalorganic chemical vapor deposition (MOCVD), and subsequent regrowth as a method to reduce the dislocation density. A 2.0 µm template layer was grown first, followed by either 2 second or 30 second etching of the GaN in KOH, followed by regrowth of 2 µm of GaN and 0.2 µm of p-type GaN. Atomic force microscopy (AFM) images showed that hexagonal pits were opened up by the KOH etch. Deep level transient spectroscopy (DLTS) measurements showed several traps present, including a dominant electron trap at 0.585 eV, with capture cross section of 1.0 × 10–15 cm2 and concentration of 1016/cm3. Another electron trap was also measured in the same range (0.536 eV, 5.7 × 10–16 cm2) with an order of magnitude lower concentration. From the DLTS measurements, the KOH dislocation etching did not significantly reduce the concentration of defects, or eliminate any specific traps. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)