In situ X-ray measurement of changes in buried structure during crystal growth

In situ synchrotron X-ray diffraction studies during the growth of arsenide and nitride semiconductors are presented. The large penetration depth of X-rays was exploited for revealing structural changes at buried interfaces as well as near the surface. Experiments were performed at a synchrotron beamline, BL11XU, SPring-8, using a molecular-beam epitaxy chamber integrated with a high-precision X-ray diffractometer. A high-speed X-ray reciprocal space mapping technique was applied to a variety of heteroepitaxial systems including InGaAs on GaAs(001), InGaAs on GaAs(111)A and GaN on SiC(0001). Results showed that even layers as thick as 200 nm were not necessarily stable even after being buried under an overlayer but could undergo significant structural changes during growth.