E se non che di cid son vere prove A nd were it not for the true evidence Per piti e piti autori, che sa,ra. nno Of many authors who will be Per i miei versi nominati altrove, Mentioned elsewhere in my rhyme Non presterei alla penna 10. mana I would not lend my hand to the pen Per nota1' cid ch'io vidi, can temenza And describe my observations, for fear ehe non fosse do. altri casso e van 0; That they would be rejected and in vane; Mala lor chiara. e vera. esperienza But these authors' clear and true experience Mi assicura. nel dir, come persone Encourages me to report, since they Degne di fede ad ogni gra. n sentenza. Should always be trusted for their word. [From" Dittamondo", by Fazio degli UbertiJ Heterojunction interfaces, the interfaces between different semiconducting materi­ als, have been extensively explored for over a quarter of a century. The justifica­ tion for this effort is clear - these interfaces could become the building blocks of lllany novel solid-state devices. Other interfaces involving semiconductors are al­ ready widely used in technology, These are, for example, metal-semiconductor and insulator-semiconductor junctions and hOll1ojunctions. In comparison, the present applications of heterojunction int. erfaces are limited, but they could potentially becOlne lnuch lllore ext. ensive in the neal' future. The path towards the widespread use of heterojunctions is obstructed by several obstacles.

G. Margaritondo, Electronic Structure of Semiconductor Heterojunctions.- Reprinted Articles.- R.L. Anderson, Solid-State Electron. (1962).- A.C. Gossard, J. Quantum Electron. (1986).- L. Esaki, J. Quantum Electron. (1986).- F. Capasso, Ann. Rev. Mat. Sci. (1986).- F. Capasso et al. , IEEE J. Quantum Electron. (1986).- H. Kroemer, Surface Sci. (1983).- D.V. Lang et al. , Appl. Phys. Lett. (1986).- P. Perfetti et al. , Appl. Phys. Lett. (1978).- R.S. Bauer et al. , J. Vac. Sci. Technol. (1978).- R.W. Grant et al. , Phys. Rev. Lett. (1978).- G. Abstreiter et al. , Physica (1985).- R. Dingle et al. , Phys. Rev. Lett. (1974).- J.L. Freeouf et al. , Appl. Phys. Lett. (1981).- J.L. Freeouf et al. , Surface Sci. (1986).- D.W. Niles et al. , Phys. Rev. (1986).- R.C. Miller et al. , Phys. Rev. (1984).- S.-H. Wei et al. , Phys. Rev. Lett. (1987).- D.G. Kilday et al. , Phys. Rev. (1987).- W. Harrison, J. Vac. Sci. Technol. (1977).- J. Tersoff, Phys. Rev. Lett. (1984).- J. Tersoff, Phys. Rev. (1984).- G. Margaritondo, Phys. Rev. (1985).- W. Harrison et al. , J. Vac. Sci. Technol. (1986).- F. Flores et al. , J. Phys. (1979).- M. Cadorna et al. , Phys. Rev. (1987).- W. Pickett et al. , Phys. Rev. (1978).- C.G. Van de Walle et al. , Phys. Rev. (1987).- S. Massidda et al. , Phys. Rev. (1987).- M.J. Caldas et al. , Appl. Phys. Lett. (1984).- J.R. Waldrop et al. , Phys. Rev. Lett. (1979).- A.D. Katnani et al. , Phys. Rev. (1983).- D.W. Niles et al. , J. Vac. Sci. Technol. (1986).- W. Mönch, Phys. Rev. Lett. (1987).- L.M. Classen et al. , Phys. Rev. Lett. (1986).- F. Capasso et al. , J. Vac. Sci. Technol. (1985).- D.W. Niles et al. , Appl. Phys. Lett. (1985).- P. Perfetti et al. , Phys. Rev. Lett. (1986).- References: Reprinted Articles.- Other References.