Bell Telephone Laboratories

Raymond Dingle

Arthur C Gossard

Pierre M Petroff

Horst L Stormer

William Wiegmann

Charles H Henry

Suitably modified molecular beam epitaxy (MBF) techniques are used to synthesize single crystal, periodic monolayer superlattices of semiconductor alloys on single crystal substrates maintained below a critical growth temperature. Described is the fabrication of periodic structures of (GaAs).sub.n (AlAs).sub.m, where m and n are the number of contiguous monolayers of GaAs and AlAs, respectively, in each period of the structure. As many as 10,000 monolayers were grown in a single structure. Also described is the MBE growth of (Al.sub.x Ga.sub.1-x As).sub.n (Ge.sub.2).sub.m, quasi-superlattice and non-superlattice structures depending on the particular values of n, m and the growth temperature. Waveguides, heterostructure lasers and X-ray reflectors using some of the structures are also described.

Method of fabricating periodic monolayer semiconductor structures by

Suitably modified molecular beam epitaxy (MBE) techniques are used to synthesize single crystal, periodic monolayer superlattices of semiconductor alloys on single crystal substrates maintained below a critical growth temperature. Described is the fabrication of periodic structures of (GaAs).sub.n (AlAs).sub.m, where m and n are the number of contiguous monolayers of GaAs and AlAs, respectively, in each period of the structure. As many as 10,000 monolayers were grown in a single structure. Also described is the MBE growth of (Al.sub.x Ga.sub.1-x As).sub.n (Ge.sub.2).sub.m, quasi-superlattice and non-superlattice structures depending on the particular values of n, m and the growth temperature. Waveguides, heterostructure lasers and X-ray reflectors using some of the structures are also described.

Periodic monolayer semiconductor structures grown by molecular beam

The mobility of a relatively narrow bandgap semiconductor material can be significantly enhanced by incorporating it into a multilayered structure (10) comprising a first plurality of relatively narrow bandgap layers (12) of the material and a second plurality of wider bandgap semiconductor layers (14) interleaved with and contiguous with the first plurality. The wide bandgap and narrow bandgap layers are substantially lattice-matched to one another, and the wide bandgap layers are doped such that the impurity concentration-thickness product therein is greater than the same product in the narrow bandgap layers. The fabrication of the structure by MBE to enhance the mobility of GaAs is specifically described. In this case, the narrow bandgap layers (12) comprise GaAs and are unintentionally doped to about 10.sup.14 /cm.sup.3, whereas the wide bandgap layers (14) comprise AlGaAs doped n-type to about 10.sup.16 to 10.sup.18 /cm.sup.3. The incorporation of this structure in an FET is also described.

Method of making high mobility multilayered heterojunction devices

High mobility multilayered heterojunction devices employing modulated

Described is a heterostructure semiconductor laser comprising a pair of wide bandgap layers having an active region sandwiched therebetween characterized in that the active region includes a plurality of thin narrow bandgap active layers interleaved with a plurality of thin relatively wider bandgap passive layers. The passive layers are thin enough (e.g., about 10-500 Angstroms) to permit electrons to distribute among the active layers either by tunneling through, or by hopping over, the energy barriers created by the passive layers. The active layers are thin enough (e.g., about 10-500 Angstroms) to separate the quantum levels of electrons confined therein. These lasers exhibit wavelength tunability by changing the thickness of the active layers. Also described is the possibility of threshold reductions resulting from modification of the density of electron states.

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Raymond Dingle