Monthly Archives: June 2014

Analytical relationship between subthreshold swing of thermionic and tunnelling currents

An analytical relationship between the subthreshold swing of the thermionic current and the tunnelling current is derived for double-gate metal–oxide semiconductor field-effect transistors (MOSFETs), based on the Wentzel-Kramers-Brillouin approximation. This formula allows predicting the behaviour of an ultimately scaled MOSFET in the subthreshold regime, as well as the performance of III–V devices.

Two-stage hot-carrier-induced degradation of p-type LDMOS transistors

Hot-carrier-induced device degradation of high-voltage p-type lateral diffused metal–oxide semiconductor (LDMOS) transistors is investigated. A two-stage linear region drain current (IDlin) shift (IDlin shift increases rapidly at the beginning of stress but tends to saturate when the stress time is longer) is observed. Technology computer-aided-design simulations and direct current current–voltage measurement results suggest that the decrease of residual fabrication interface traps (NIT) leads to an initial increase in IDlin shift. On the other hand, two competing mechanisms, i.e. increase in NIT generation and increase in electron trapping, are responsible for the saturated IDlin shift when the stress time is longer.

Flexible x-ray imaging detector based on direct conversion in amorphous selenium

In this paper, the authors propose a mechanically flexible direct conversion x-ray detector as a potential solution for portable and conformal digital x-ray imaging. It consists of a micropillar structured layer of 100-μm-thick amorphous selenium (a-Se) on a flexible thin film transistor (TFT) backplane with a pixel size of 70 μm as a substrate. The flexible substrate is made of an optically transparent polyimide with a heat resistance of more than 200 °C. It is bonded on a glass carrier for rigid substrate handling during the amorphous silicon (a-Si) TFT process. Separating the flexible substrate from the glass carrier is partly facilitated by a debonding layer sandwiched between them. A two-dimensional electrical simulation analysis revealed a possible charge generation and collection mechanism within the micropillared a-Se layer. An x-ray image captured by the curved flexible detector indicated that a pillarlike a-Se conversion layer can be used to perform x-ray imaging. This is, to the best of our knowledge, the first demonstration of a flexible digital x-ray direct conversion detector.