Faulty composition of nitride semiconductor epitaxial substrates for electron devices

NTT Advanced Technology Corporation has been manufacturing and selling "nitride semiconductor epitaxial substrates," which are expected to have applications in high power amplifiers and high voltage power converters used in mobile base stations of third, and subsequent, generation mobile communication systems.
Recently, we have sold "InAlN/GaN epitaxial substrates" for research and development purposes. However, it has been found that its composition is not as intended, but is AlGaN/GaN. ^(*Note)
We sincerely apologize for the great inconvenience the sale of these nitride semiconductor epitaxial substrates with unintended composition has caused to our customers.
We are currently examining how the crystal growth mechanism used has led to the growth of an AlGaN layer instead of the intended InAlN layer.
In order to prevent such faulty products from being shipped again, we are modifying our shipping inspection method to include composition analysis in addition to the existing X-ray analysis and electron concentration measurement.