Growth techniques to reduce V-defect density in GaN and AlGaN layers grown on 200 mm Si (111) substrate.

V-defects can be very detrimental to the functionality of GaN based light emitting diodes (LEDs) and high power transistors grown on 200 mm Si (111) substrates. This work focuses on reducing these detrimental defects in the GaN/AlGaN/AlN stacks grown in a Veeco Turbodisc Maxbright MOCVD system. The origins of V-defects in GaN/AlGaN/AlN material were studied by cross-sectional transmission electron microscope (TEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). It was found that V-defects were associated with inversion domain boundary (IDB) like defects, which started from the interface between the AlN nucleation layers and the Si (111) substrates. These IDB-like defects were terminated by generating V-defects in the upper layers. Encouraging the 2-D GaN growth mode helped to close these V-defects in the GaN layers, but relaxed the built-in compressive stress faster and resulted in excessive wafer bow. Optimizing the V/III ratio during the AlN nucleation step improved AlN crystal quality and surface morphology, and close V-defects in GaN without degrading wafers stress condition. [ABSTRACT FROM AUTHOR]