1. J. O. Borland and C. I. Drowley, Solid State Technology, Au- gust 1985, p. 141.
2. N. Kasai, N. Endo, A. Ishitani, and H. Kitajima, IEDM Tech. Digest, 419 (1985).
3. N. Endo, N. Kasai, A. Ishitani, H. Kitajima, and Y. Kurogi, IEEE Trans. Electron. DevicesED-33, 1659 (1986).
4. S. Nagao, K. Higashitani, Y. Akasaki, and H. Nakata, IEEE Trans. Electron DevicesED-33, 1738 (1986).
5. T. Yamada, S. Samata, H. Takato, and Y. Matsushita, IEDM Tech. Digest, 35 (1989).