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The remarkable developments in fine line lithography and new epitaxial technologies of MBE and MOCVD have generated significant possibilities of fabricating various types of 2D structures, viz. ultrathin films, inversion layers etc. In ultrathin films where the width of the films are comparable to the de Broglie wave length of the carriers, 'the restriction of the motion of the carriers in the direction normal to the film (say, the z-direction) may be viewed as carrier confinement in an infinitely deep 1D square potential well, leading to the quantization (known as quantum size effect (qv)) of the wavevector, allowing 21) electron transport parallel to the film representating new characteristics not exhibited in bulk semiconductors. Heterostructures based on different materials are currently widely investigated because of the enhancement of the carrier mobility. Though many new effects associated with size quantization have been already reported, neverthe-less, it appears from the literature that the photoemission from ultrathin films of small gap optical materials has yet to be studied. We shall take ultrathin films of n-CdGeAs2) as an example, though from our generalized expressions, the well-known special resalts for wide gap materials can be derived. The above class of compounds are being increasingly used as non-linear optical materials and light emitting diodes. We have formulatW the photoemission from ultrathin films of n-CdGeAs, by deducing a new dispersion law, within the framework of k formalism, taking into account various types of anisotropies in the energy spectrum. It is found, that the photoemission increases with incident photon energy in a ladder like manner and also exhibits oscillatory dependence with changing film thickness and surface electron concentration respectively. The corresponAing results for isotropic parabolic energy bands have also been obtained as special cases of our generalized results.
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