1. N. P. Esina, N. V. Zotova, B. A. Matveev, et al., Pis’ma Zh. Tekh. Fiz. 9(7), 391 (1983) [Sov. Tech. Phys. Lett. 9, 167 (1983)].
2. B. Matveev, N. Zotova, S. Karandashov, et al., IEE Proc.: Optoelectron. 145(5), 254 (1998).
3. A. A. Popov, V. V. Sherstnev, Yu. P. Yakovlev, et al., Electron. Lett. 33, 86 (1997).
4. A. A. Popov, M. V. Stepanov, V. V. Sherstnev, and Yu. P. Yakovlev, Pis’ma Zh. Tekh. Fiz. 24(15), 34 (1998) [Tech. Phys. Lett. 24, 596 (1998)].
5. A. Krier, H. H. Gao, V. V. Sherstnev, and Yu. P. Yakovlev, J. Phys. D (2001) (in press).