Use of Sub-nanometer Thick AlN to Arrest Diffusion of Ion-Implanted Mg into Regrown AlGaN/GaN Layers

Diffusion of Mg from Mg-ion-implanted GaN layer to metalorganic chemical vapor deposition (MOCVD) regrown AlGaN/GaN layers was detected and identified as a critical problem in devices which are dependent on layers implanted with Mg for its current blocking properties. Surface treatments done to etch away the Mg rich layer prior to the regrowth was not beneficial unlike in the case of the GaN doped with Mg. Remarkably, regrowth of a sub-nanometer thick (7 Å) AlN layer on top of the Mg-implanted GaN was found to be effective in arresting the Mg from diffusing out into the AlGaN/GaN layers grown on top at 1160 °C. This was verified from both secondary ion mass spectrometry (SIMS) analysis and electrical (capacitance–voltage) data. This result is significant because at such thickness the AlN would not impact the crystal quality of the overgrown material and serve as a viable method of achieving a current blocking structure by MOCVD growth technique.

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