Random diode arrays and mesoscale physics of large-area semiconductor devices

Abstract

Large-area, thin-film semiconductor devices often exhibit strong fluctuations in electronic properties on a mesoscale level that originate from relatively weak microscopic fluctuations in material structures such as grain size, chemical composition, and film thickness. Amplification comes from the fact that electronic transport through potential barriers is exponentially sensitive to the local parameter fluctuations. These effects create new phenomena and establish the physics of large-area, thin-film devices as a distinctive field of its own, quite different from that of microelectronics. We show that (i) large-area semiconductor thin-film devices are intrinsically nonuniform in the lateral directions, (ii) the nonuniformity can span length scales from millimeters to meters depending on external drivers such as light intensity and bias, and (iii) this nonuniformity significantly impacts the performance and stability of, e.g., photovoltaics, liquid crystal displays, and light emitting arrays. From the theoretical standpoint our consideration introduces a new class of disordered systems, which are random diode arrays. We propose a theory describing one class of such arrays and derive a figure of merit that characterizes the significance of nonuniformity effects. Our understanding suggests some methods for blocking the effects of nonuniformities.