Exafs Studies of Group III-Nitrides

Abstract

ABSTRACTThe group III nitrides have important applications for blue/green LEDs, blue/UV laser diodes and for high-power high frequency FETs. In all such devices the alloys play an important role either in the active part of the structure or in the cladding regions. The properties of the group III-nitride alloys are not at present well understood and in particular there are indications that phase separation can occur. We have undertaken a comprehensive study of (InGa)N alloys using EXAFS in order to study such problems.We have demonstrated recently that REFLEXAFS technique can be used to give interatomic distances for (InGa)N alloys using the In edge to measure the bond lengths as a function of In content over the complete range from InN to GaN. We have now extended this study by using the Total Electron Yield (TEY) EXAFS technique to study the bond lengths by using both the Ga and In edges for (InGa)N alloys. The TEY data for the (InGa)N alloy samples gives more reliable data for the In-In and In-Ga separations than the earlier REFLEXAFS studies. Data obtained for the In-Ga separation from the Ga and In edges agree well within experimental error.The data obtained from this study suggest that the (InGa)N samples grown at low temperature do not exhibit evidence for phase separation.