1. R. P. Huebener, J. Parisi, and J. Feinke, Appl. Phys. A 48, 107 (1989).
2. L. L. Golik, M. M. Gutman, and V. E. Paskeev, Phys. Status Solidi B 162, 199 (1990).
3. E. Echoll, Appl. Phys. 48, 95 (1989).
4. É. S. Kachlishvili and I. D. Kezerashvili, Fiz. Tekh. Poluprovodn. 24, 1106 (1990) [Sov. Phys. Semicond. 24, 697 (1990)].
5. V. V. Vladimirov and V. N. Gorshkov, Fiz. Tekh. Poluprovodn. 14, 417 (1980) [Sov. Phys. Semicond. 14, 247 (1980)]; V. V. Vladimirov, P. M. Golovinsk $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} $$ , and V. N. Gorshkov, Fiz. Tekh. Poluprovodn. 15, 40 (1981) [Sov. Phys. Semicond. 15, 23 (1981)]; V. V. Vladimirov, V. N. Gorshkov, and V. K. Malyutenko, Fiz. Tekh. Poluprovodn. 26, 1580 (1992) [Sov. Phys. Semicond. 26, 887 (1992)].