MOCVD Growth of InN using ArF Excier Laser

ArF准分子激光MOCVD生长技术（LA-MOCVD）是一种获得高质量InN薄膜的新方法，这种生长技术可以在较宽的生长温度范围内沉积，从室温（RT）到极高温度（700℃）通过在衬底表面上的选定区域中辐射激光束，在低生长温度下获得了InN的选择性区域生长。使用非常少量的NH3流（约100 sccm），磨损小于0.5μm/h。成功地生长出了结晶质量好、表面形貌好的单晶InN薄膜，并对薄膜的电学性能进行了测试。MOCVD生长的InN薄膜与最近报道的良好结果相比仍然很差。阐明了InN薄膜电学性能差的主要原因。对InN的实际带隙能量进行了测定。讨论了InN薄膜电学性能差的原因InN的带隙值的显著变化已经被清楚地研究。已经发现，即使在单晶膜的情况下，InN生长膜中的氧污染也是较大的带隙吸收能量值的原因。在低温生长的膜中，氧的掺入显著增强并且似乎作为合金存在，这导致较大的吸收边缘。然而，在较高温度下生长的膜中，氧作为施主存在，并由于Burstein-Moss位移而引起较大的吸收边，从而得出InN的实际光学带隙能量约为0.7eV的结论。

The MOCVD growth technique using an ArF excier laser (LA-MOCVD) has been developed as a new potential approach to obtain high qiial ity InN film.This growth technique enables deposition over a wide range of growth temperatures, ranging from room temperature (RT) to a very high temperature (700℃).Selective area growth of InN has been obtained at low growth temperature by radiating the laser beam in a selected area on the substrate surface.The technique provides a InN growth rate of wore than 0.5μm/h using a very little amount (〜100 sccm) of NH3 flow. Single crystalline InN films with good crystalline quality and excellent surface morphology have been successfully grown.The electrical properties of the LA-MOCVD grown InN films are still found to be poor compared to the recently reported good results.Important evidences as to what species is responsible for poor electrical properties in the grown InN are clarified.Effort has been made for determining the actual band gap energy of InN.The causes of the significant variation in the band gap value of InN have been clearly studied.Oxygen contamination in the InN grown film has been found to be a cause of a larger band gap absorption energy value even in the case of single crystalline film.In low temperature grown films, oxygen incorporation was significantly enhanced and seemed to exist as an alloy, which caused a larger absorption edge.Whereas, in films grown at higher temperatures, oxygen existed as a donor and caused a larger absorption edge due to a Burstein-Moss shift.This evaluation enables the conclusion that the actual optical band gap energy of InN is about 0.7 eV.