[1] Bhuiyan A G, Hashimoto A and Yamamoto A 2003 J. Appl.
Phys. 94 2779

[2] Fareed R S Q, Gaska R and Shur M S 2004 J. Appl.
Phys. 95 7998

[3] Wu J, Walukiewicz W, Yu K M, Ager III J W, Haller E E, Lu
H, Schaff W J, Saito Y and Nanishi Y 2002 Appl. Phys. Lett.
80 3967

[4] Yu K M, Liliental-Webber Z, Walukiewicz W, Shan W, AgerIII
J W, Li S X, Jones R E, Haller E E, Lu H and Schaff W J 2005
Appl. Phys. Lett. 86 071910

[5] Matsuoka T, Okamoto H, Nakao M, Harima H and Kurimoto E
2002 Appl. Phys. Lett. 81 1246

[6] Feng Z X, Yao S D, Hou L N and Jin R Q 2005 Nucl.
Instrum. Methods Phys. Res. B 229 246

[7] Butcher K S A and Tansley T L 2005 Superlattices
Microstruct. 38 1

[8] Wu M F, Zhou S Q, Vantomme A, Huang Y, Wang H and Yang H
2006 J. Vac. Technol. A 24 275

[9] Wu M F, Vantomme A, Hogg S M and Langouche G 1999
Appl. Phys. Lett. 74 366

[10] Wu M F, Yao S D, Vantomme A, Hogg S, Langouche G, Van der
Stricht W, Jacobs K, Moerman I, Li J and Zhang G Y 2000 Mater.
Sci. Eng. B 75 232

[11] Pan C K, Zheng D C, Finstad T G, Chu W K, Speriosu V S,
Nicolet M A and Barrett J H 1985 Phys. Rev. B 31 1270