Zincblende and wurtzite phases in InN epilayers and their respective band transitions

Zincblende and wurtzite phases of InN are found in InN epilayers deposited by molecular beam epitaxy on GaN buffers which were grown by metal organic chemical vapor deposition. Valence electron energy loss spectroscopy (VEELS) was applied to determine band transitions in both phases of InN. GaN buffer layers were used as VEELS reference. The chemistry and crystalline structure of the observed areas was recorded simultaneously to exclude a contribution from oxides and/or metal clusters or extended defects such as grain boundaries. At room temperature a band transition for wurtzite InN was found at (1.7 ± 0.2) eV and for zincblende InN at (1.4 ± 0.2) eV that are ascribed to the fundamental bandgaps of the respective polytypes. Those values correlate well with recent results of various research groups measuring the bandgap in InGaN alloys with VEELS.