Reduction of threading dislocations in RF-MBE grown polarity controlled GaN by AlN multiple interlayers

Crystal quality of polarity controlled GaN layers, both in Ga- and N-polarity grown by RF-plasma assisted molecular beam epitaxy (RF-MBE) were improved by introducing the high-temperature grown AIN multiple intermediate layers (HT-AIN-MIL). The character and the propagation behavior of threading dislocations were investigated for the Ga- and N-polar layers by transmission electron microscopy (TEM). In a Ga-polar layer, edge-type dislocations were dominant and dislocations were propagated perpendicular to the substrate/epitaxial layer interface. And the dislocations were effectively filtered by HT-AIN-MIL. For the case of N-polar GaN, edge- and mixed-type dislocations were dominant with an even ratio. The dislocations were also filtered by HT-AIN-MIL and bent and join together by passing through the HT-AIN-MIL. By introduction of HT-AIN-MIL, the electron mobility was improved to 332 cm(2)/Vs for a Ga-polar layer and 668 cm(2)/Vs for an N-polar layer, respectively.