[1] Johnson J L, Samoska L A., Gossard A C., Merz J, Jack M D,
Chapman G R, Baumgratz B A, Kosai K and Johnson S M 1996 J.
Appl. Phys. 80 1116

[2] Fuchs F, Weimar U, Pletschen W, Schmitz J, Ahlswede E,
Walther M, Wagner J and Koidl P 1997 Appl. Phys. Lett.
71 3251

[3] Rehm R, Walther M, Schmitz J, Flei{\ssner J, Fuchs F,
Ziegler J and Cabanski W 2005 SPIE 5957 595701

[4] Zhang X B, Ryou J H, Dupuis R D, Petschke A, Mou S, Chuang
S L, Xu C and Hsieh K C 2006 Appl. Phys. Lett. 88 072104

[5] Rodriguez J B, Christol P, Ouvrard A, Chevrier F, Grech P
and Joullie A 2005 Electron. Lett. 41 362

[6] Mohseni H, Tahraoui A, Wojkowski J, Razeghi M, Brown G J,
Mitchel W C and Park Y S 2000 Appl. Phys. Lett. 77 1572

[7] Mohseni H, Wojkowski J, Razeghi M, Brown G and Mitchel W
1999 IEEE J. Quantum Electron. 35 1041

[8] Blank H, Thomas M, Wong K and Kroemer H 1996 Appl.
Phys. Lett. 69 2080

[9] Hao R T, Xu Y Q, Zhou Z Q, Ren Z W, Ni H Q, He Z H and Niu
Z C 2007 J. Phys. D: Appl. Phys. 40 1080

[10] Bracker A S, Yang M J, Bennett B R, Culbertson J C and
Moore W J 2000 J. Cryst. Growth 220 384

[11] Hao R T, Xu Y Q, Zhou Z Q, Ren Z W, Ni H Q, He Z H and
Niu Z C 2007 J. Phys. D: Appl. Phys. 40 6690

[12] Balakrishnan G, Tatebaysshi J, Khoshakhlagh A, Huang S H,
Jallipalli A, Daswon L R and Huffaker D L 2006 Appl. Phys.
Lett. 89 161104

[13] Steinshnider J, Harper J, Weimer M, Lin C H, Pei S S and
Chow D H 2000 Phys. Rev. Lett. 85 4562

[14] Steinshnider J, Weimer M, Kaspi R and Turner G W 2000
Phys. Rev. Lett. 85 2953

[15] Renard C, Marcadet X, Massies J, Pr\'{evot I, Bisaro R
and Galtier P 2003 J. Cryst. Growth 259 69

[16] Dente G C and Tilton M L 1999 J. Appl. Phys.
86 1420

[17] Hall K C, Gundogdu K, Altunkaya E, Lau W H, Flatte M E,
Boggess T, Zinck J J, arvos-Carter W B and Skeith L 2003 Phys.
Rev. B 68 115311

[18] Szmulowicz F, Haugan H, and Brown G J 2004 Phys.
Rev. B 69 155321

[19] Zhen H L, Li N, Xiong D Y, Zhou X C, Lu W and Liu H C
2005 Chin. Phys. Lett. 22 1806