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High crystalline quality thick films of single crystal CdTe were grown directly on (211) Si substrates using MOVPE growth technique for gamma ray detector fabrication. A highest growth-rate of 65 [micro]m/h was achieved at a substrate temperature of 600[degrees]C. Films were monocrystalline as confirmed from the x-ray diffraction pattern. Results from the 4.2 K photoluminescence measurement showed films were of good crystalline quality. The gamma detector was fabricated in a p--CdTe/n--CdTe/[n.sup.+]--Si heterojunction diode structure, which exhibited clear rectifying behavior with a low value of room-temperature reverse bias leakage current, typically 0.11 [micro]A/[cm.sup.2] at 100 V bias. The detector leakage current was reduced by three orders of magnitude from the room-temperature value at -30[degrees] C. The detector clearly demonstrated its spectroscopy capability by resolving energy peaks from the [sup.241]Am gamma isotope. Index Terms--CdTe thick films, gamma ray detector, heteroepitaxy, medical imaging, MOVPE growth.

Mathematical models, in which many input variables are involved, require a range of input and output data, since the number of parameters increases with the input variables. GMDH (Group Method of Data Handling) has been used for the identification of a mathematical model that has many input variables but limited data needs by using a hierarchical structure. This paper proposes a neuro-fuzzy (GMDH model, adopting Gaussian radial basis functions (GRBF) as partial descriptions of GMDH. GRBF is reinterpreted as both a simplified fuzzy reasoning model and as a three-layered neural network. As an example of applying the algorithm, the wheel wear equation is identified, using data from experiments of abrasive cut-off. In the model, characteristics of work materials, grinding fluids, factors of wheels, wheel velocity and table feed are used as input variables, and the grinding ratio is the resulting output. The validity of the model is confirmed within the predicted accuracy by using additional data. [ABSTRACT FROM AUTHOR]