Crystallographic Wet Chemical Etching of Semipolar GaN (11–22) Grown on <I>m</I>-Plane Sapphire Substrates

Abstract

This paper reports the etch rates and etched surface morphology of semipolar GaN using a potassium hydroxide (KOH) solution. Semipolar (11-22) GaN could be etched easily using a KOH solution and the etch rate was higher than that of Ga-polar c-plane GaN (0001). The etch rate was anisotropic and the highest etch rate was measured to be approximately 116 nm/min for the (1011) plane and 62 nm/min for the (11-20) plane GaN using a 4 M KOH solution at 100 °C, resulting in specific surface features, such as inclined trigonal cells.

Effect of Native Oxide Layer on Mechanochemical Reaction at the GaN–Al2O3 Interface

“…Such reactions can hardly occur under pure thermodynamics or mechanics but can be activated by external mechanical energy. Thus, the mechanochemical activation energy ( E a ) at the GaN–Al 2 O 3 interface is considerably larger than the thermal energy (~ RT , where R is the gas constant with a value of 8.314 J/K, and T is equal to 300 K at room temperature) (Stocker et al, 1998 ). Under the shear force of the Al 2 O 3 microsphere, E a can be physically lowered by the external mechanical energy, and the reduction magnitude in E a is represented as E m (Beyer and Clausen-Schaumann, 2005 ; Peguiron et al, 2016 ).…”