This work was supported by a Defense Advanced Research Projects Agency /Office of Naval Research University Research Initiative Program N00014-86-K0760, by the Office of Naval Research under contract No. N0014-87-K0522, and by the Air Force Office of Scientific Research under grant No. 85-0185.


The use of ZnSe on GaAs epilayers (epi) as a pseudo-insulator in field effect device applications is demonstrated. The passivating ZnSe layers are grown on GaAs(epi) by interrupted growth molecular beam epitaxy (MBE) using two separate MBE machines. A thin layer of amorphous arsenic protects the GaAs(epi) during transfer between the MBE systems. When nucleated on the GaAs(epi), the ZnSe grows layer-by-layer as revealed by the reflection high energy electron diffraction pattern generated in the II-VI MBE growth chamber. A study of intensity oscillations in the electron diffraction pattern is further used to understand the initial growth stages of ZnSe on GaAs(epi). The material properties of the ZnSe/GaAs(epi) heterostructure are briefly examined. Even though ZnSe and GaAs have a 0.25% lattice mismatch, transmission electron micrographs show that very thin films (1OOOA) of ZnSe form a coherent and dislocation free interface with the GaAs(epi). In thicker ZnSe films, strain relieving misfit dislocations are observed. Photoluminescence measurements reveal information about the effect of the lattice mismatch on the energy band structure of the ZnSe. For the 1OOOA film, the excitonic features are shifted upwards in energy, and the normally degenerate light and heavy hole valence bands split into two bands. As the 1OOOA of ZnSe is an appropriate thickness for an insulator in a field-effect device, the ZnSe/ GaAs(epi) heterostructure is then used in metal-insulator-semiconductor (MIS) capacitors and transistors. Most prominent, the fabrication of the first depletion-mode field-effect transistors based on the ZnSe/n-GaAs heterointerface are described. The transistors display near ideal characteristics with complete current saturation and cutoff; the channel modulation indicates th a t the Fermi level is not pinned a t the ZnSe/n-GaAs interface. With the success of the depletion-mode transistors, the use of ZnSe and GaAs(epi) in future MIS devices appears promising

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