AVS 47th International Symposium
    Processing at the Nanoscale/NANO 6 Wednesday Sessions
       Session NS+NANO6-WeP

Paper NS+NANO6-WeP5
Etching of GaN (0001) with Halogens: Pit Growth and Step Etching by Cl

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: K.S. Nakayama, Tohoku University, Japan
Authors: K.S. Nakayama, Tohoku University, Japan
S. Kuwano, Tohoku University, Japan
Q.Z. Xue, Tohoku University, Japan
Q.K. Xue, Chinese Academy of Science
T. Sakurai, Tohoku University, Japan
Correspondent: Click to Email
We have studied the etching of GaN (0001) by Cl using scanning tunneling microscopy (STM) to obtain morphological information that can be related to surface reaction and desorption pathway. We used N- and Ga- polar GaN surfaces prepared by N-plasma-assisted molecular beam epitaxy (MBE) followed by Ga deposition. A Ga rich GaN(0001) surface was exposed to molecular Cl@sub 2@ at room temperature for the coverage of more than 1 monolayer. Heating to 600-700 °C induced etching by thermal desorption. STM images show that smooth and rough steps appeared and these triangle pits were initiated on the terrace after the thermally activated reaction. The height profiles of a pit and a step in the STM images reveal layer-by-layer removal of GaN. The etching directions of steps can be attributed to the number of dangling bond at the step edges. We also discuss possible desorption pathways with atomic scale including the formation of volatile GaClX products and the spontaneous desorption of nitrogen molecule. When the Ga atom on the top layer removed by Cl, the nitrogen atom in the second layer appeared having two dangling bonds. This configuration would be energetically unfavorable and the distance of dangling bonds of neighboring nitrogen atoms is very close. Therefore, the nitrogen atoms would combine each other to form nitrogen molecules and the spontaneous desorption would occur on the surface.