A noncoplanar mesh design that enables electronic systems to achieve large, reversible levels stretchability ͑Ͼ100%͒ is studied theoretically and experimentally. The design uses semiconductor device islands and buckled thin interconnects on elastometric substrates. A mechanics model is established to understand the underlying physics and to guide the design of such systems. The predicted buckle amplitude agrees well with experiments within 5.5% error without any parameter fitting. The results also give the maximum strains in the interconnects and the islands, as well as the overall system stretchability and compressibility.
AlGaN ∕ GaN ∕ SiC Schottky barrier diodes (SBDs), with and without Si3N4 passivation, have been characterized by temperature-dependent current-voltage and capacitance-voltage measurements, and deep level transient spectroscopy (DLTS). A dominant trap A1, with activation energy of 1.0 eV and apparent capture cross section of 2×10−12cm2, has been observed in both unpassivated and passivated SBDs. Based on the well-known logarithmic dependence of DLTS peak height with filling pulse width for a line-defect related trap, A1, which is commonly observed in thin GaN layers grown by various techniques, is believed to be associated with threading dislocations. At high temperatures, the DLTS signal sometimes becomes negative, likely due to an artificial surface-state effect.
One important aspect of stretchable electronics design is to shield the active devices from strains through insertion of a soft layer between devices and substrate. An analytical model is established, which gives linear dependence of strain isolation on the reciprocal of strain-isolation layer thickness, and the reciprocal of device and substrate stiffness. Strain isolation is also linearly proportional to the shear modulus of strain-isolation layer and square of device length.
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