Characterization of traps in InAlN by optically and thermally stimulated deep level defect spectroscopies

摘要

Deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) were used to characterize defect states throughout the bandgap of unintentionally-doped InxAl1-xN grown by metal organic chemical vapor deposition for x = 0.18 (nominally lattice-matched) and x = 0.15 compositions. DLTS revealed broad peaks with energy levels of E-C - 0.23 eV and 0.38 eV for In0.18Al0.82N and In0.15Al0.85N, respectively, tracking the difference in their conduction band minima [S. Schulz et al., Appl. Phys. Express 6, 121001 (2013)]. Capture kinetics studies revealed logarithmic filling behavior, which with the broad peaks, implies that an extended defect source is likely, consistent with threading dislocation densities (TDD) of similar to 1 x 10(9) cm(-2) measured for both structures. However, the trap concentration did not track the detailed TDD variation but instead followed the background oxygen content, which varied between 1.2 x 10(18) cm(-3) and 1.8 x 10(18) cm(-3) for the samples. Taken together with the logarithmic capture kinetics, this implies that dislocation-oxygen complexes could be the source for this trap. In spite of the high oxygen content in the samples, this state did not reveal DX-like behavior, supporting the assertion of an oxygen-dislocation complex as its likely source. DLOS also revealed additional states at EC -1.63 eV, 2.09 eV, and 3.59 eV for In0.18Al0.82N and analogous states at EC -1.70 eV, 2.70 eV, and 3.90 eV within In0.15Al0.85N. Lighted capacitance-voltage measurements indicated that the near mid-gap (EC -2.09 eV and 2.70 eV) and near valence band (EC -3.59 eV and 3.90 eV) states are their primary sources for carrier compensation. Published by AIP Publishing.