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Umicore has been the leading Germanium substrate manufacturer over the last 20 years. We are only able to maintain that position by constantly improving the quality of our product. In this work, Umicore wants to present how it will continue this tradition by adding even more value to its product. In the beginning of 2014 we proposed to our customers to help them in achieving their yield improvement goals. Two main concerns were expressed: the breakage rate in their production line and non-uniform epi-growth. After two years of development, Umicore has bundled these two improvements into a new product. The ExpoGerTM wafer combines a better mechanical yield with a uniform, epi-ready surface enabling a narrower distribution of the electrical performance. The breakage rate of the customers is related to the wafers that suffer from early failure. The percentage of early failures is related to its thickness. With the trend towards even thinner substrates, it is important to add features that reduce the percentage of early failures. Two features are crucial: the shape of the substrate edge and the stress relief etch, which influences the wafer strength. Just as for the strength, two distinctive aspects define the surface quality. On the one hand, there are the number and size of surface defects, which have an important influence on the metal-organic chemical vapour deposition (MOCVD) growth performed at Umicore’s customers. On the other hand, drying marks, which are invisible to the naked eye, may lead to a local, non-uniform growth and they can be a precursor to time dependent haze issues. Umicore is able to demonstrate the impact of the ExpoGerTM processes on the strength and surface quality of its wafers and thus on the production yield of its customers.

The space charge limited currents J in conducting organic materials often show J∼V[sup m] (where m > 2) dependence on voltage V. Two models have been used extensively to understand this behavior. In one model, the mobility μ is assumed to be dependent on electric field F. In the other model, an exponential distribution of traps is assumed and the mobility is taken to be independent of field. In this model the influence of the high electric fields present in organic polymers has not been taken into account. We present a model to calculate the J(V) characteristics for single carrier organic polymers taking into account the change in the occupancy of the traps due to the high electrical fields present in these materials. We show that the field dependent trap occupancy (FDTO) model can effectively explain the current-voltage characteristics reported by several different groups. If the FDTO model is used, it is not necessary to use the two different models mentioned above. [ABSTRACT FROM AUTHOR]

Transport properties of conducting organic materials are studied. It is shown through numerical solutions that the current approaches the trap-filled limit asymptotically as the applied voltage approaches infinity.