1. Asauskas R, Dobro V and Krotkus A 1980 Sov. Phys. Semicond. 14 1377
2. Branski P I, Gorodrichi O P and Shevchenko V V 1990 Infrared Phys. 30 59
3. Carrolnand J A and Spivak J F 1966 Solid State Electron. 9 383
4. Carter M J, Anson I I, Knowles A and Hill R 1987 Proceedings of the 19th IEEE photovoltaic specialists conference (New Orleans: IEEE, NY p. 1275
5. Chang P K and Bedair S M 1985 Appl. Phys. Lett. 46 383