Structural Analysis of In _xGa_1−xN/GaN MQWs by Different Experimental Methods

Structural properties of In_xGa_1−xN/GaN multi-quantum wells (MQWs) grown on sapphire by metal organic chemical vapor deposition are investigated by synchrotron radiation x-ray diffraction (SRXRD), Rutherford backscattering/channelling (RBS/C) and high-resolution transmission electron microscopy. The sample consists of eight periods of In_xGa_1−xN/GaN wells of 2.1 nm thickness and 8.5 nm thickness of GaN barrier, and the results are very close, which verifies the accuracy of the three methods. The indium content in In_xGa_1−xN/GaN MQWs by SRXRD and RBS/C is estimated, and results are in general the same. By RBS/C random spectra, the indium atomic lattice substitution rate is 94.0%, indicating that almost all indium atoms in In_xGa_1−xN/GaN MQWs are at substitution, that the indium distribution of each layer in In_xGa_1−xN/GaN MQWs is very homogeneous and that the In_xGa_1−xN/GaN MQWs have a very good crystalline quality. It is not accurate to estimate indium content in In_xGa_1−xN/GaN MQWs by photoluminescence (PL) spectra, because the result from the PL experimental method is very different from the results by the SRXRD and RBS/C experimental methods.