Current transport and maximum dielectric strength of atomic-layer-deposited ultrathin Al2O3 on GaAs

Current-voltage characteristics have been measured for an ultrathin atomic-layer-deposited Al2O3 on GaAs as a function of film thickness, ambient temperature, and electric field. Current transport measurements indicate direct tunneling for 12–25Å ultrathin films and typical Frenkel-Poole emission for 50–60Å thick films. The maximum dielectric strength, which is of considerable importance for metal-oxide-semiconductor device applications, is studied thoroughly in this letter. The square root of the maximum dielectric strength is found to be roughly reversely proportional to the temperature from 500to300K, and becomes constant below 200K. The enhancement in the dielectric field strength observed from 300to200K for the ultrathin insulating films can be adequately described using classical models.