An effect of the position of notch-doping layer in 1-μm GaN Gunn diode on threading dislocations (TDs) distribution was investigated by transmission electron microscopy. Compared with the top-notching-layer (TNL) structure, the bottom-notching-layer (BNL) structure can efficiently reduce the TDs density and improve the crystal quality in the transit region of GaN Gunn diode because it exhibits twice-transition of growth mode from atomic step flow to layer-by-layer nucleation and leads to a significant annihilation of TDs before penetrating into the transit region. X-ray diffraction and Raman spectroscopy reveal that the BNL structure has less compressive stress than the TNL structure.

Threading Dislocation Reduction in Transit Region of GaN Terahertz Gunn Diodes. L.Li, L.A.Yang, J.C.Zhang, J.S.Xue, S.R.Xu, L.Lv, Y.Hao, M.T.Niu: Applied Physics Letters, 2012, 100[7], 072104