Effects of carrier confinement in MgZnO/CdZnO thin-film transistors: Towards next generation display technologies

Abstract

The authors propose a novel CdZnO/MgZnO single-well heterojunction thin-film transistor for achieving carrier confinement in a low potential well lying between two high potential barriers. The working mechanism of the TFT is elaborated with the help of energy band diagrams which indicate the formation of high density 2DEG at the channel/insulator interface. The effects of carrier confinement and 2DEG formation on device performance has been studied by TCAD simulation. The device exhibits an uncharacteristically sharp transition from OFF to ON states, high ON state current (10−3), low OFF state current (10−14), high mobility (8cm2/V-s) but suffers from a very narrow range of operating gate bias. In order to overcome this, a double-well heterojunction TFT is propounded as an improvement over the existing heterostructure, where two wells work in parallel to increase the range of operation substantially. The double-well TFT displays a two order increase in ON current and a two order reduction in OFF current with respect to its single-well counterpart, concomitantly achieving a four-fold increment in mobility with a peak mobility value of 32cm2/V-s.